View source for Lauda Air Flight 004

{{Short description|1991 aircraft accident in Thailand}}
{{Use dmy dates|date=May 2018}}
{{Infobox aircraft occurrence
| image           = Lauda Air Boeing 767-3Z9ER OE-LAV at Vienna International Airport, 1989.jpg
| caption         = OE-LAV, the aircraft involved in the accident, seen in 1989
| occurrence_type = Accident
| date            = {{start date|1991|05|26|df=y}}
| summary         = [[Loss of control (aeronautics)|Loss of control]] following uncommanded [[Thrust reversal|thrust-reverser]] deployment leading to [[in-flight breakup]]
| site            = [[Phu Toei National Park]], [[Suphan Buri province]], Thailand
| coordinates     = {{coord|14|56|48|N|99|27|10|E|region:TH-72_type:landmark|display=inline,title}}
| aircraft_type   = [[Boeing 767|Boeing 767-3Z9ER]]
| aircraft_name   = ''[[Wolfgang Amadeus Mozart|Mozart]]''
| operator        = [[Lauda Air]]
| tail_number     = OE-LAV
| origin          = [[Kai Tak Airport]], [[British Hong Kong]]
| stopover        = [[Don Mueang International Airport]], [[Bangkok]], Thailand
| destination     = [[Vienna International Airport]], [[Vienna]], Austria
| occupants       = 223
| passengers      = 213
| crew            = 10
| fatalities      = 223
| survivors       = 0
| IATA            = NG004
| ICAO            = LDA004
| callsign        = LAUDA 4
}}
'''Lauda Air Flight 004 (NG004/LDA004)''' was a regularly scheduled [[international passenger flight]] from [[Hong Kong]], via [[Bangkok]], Thailand, to [[Vienna]], Austria. On 26 May 1991, the [[Boeing 767#767-300ER|Boeing 767-300ER]] operating the route crashed following an uncommanded deployment of the [[Thrust reversal|thrust reverser]] on the [[Aircraft engine#Engine position numbering|No. 1 engine]] during the climb phase, causing the aircraft to enter an [[Stall (fluid dynamics)|aerodynamic stall]], uncontrolled dive, and in-flight breakup, killing all 213 passengers and ten crew members on board. It is the deadliest aviation accident involving the Boeing 767,{{efn|name=excl911|The crashes of both [[American Airlines Flight 11]] and [[United Airlines Flight 175]] are deadlier. However, both incidents are not considered as aviation accidents due to them being acts of terrorism as part of the [[September 11 attacks]].}} and the deadliest aviation accident in Thailand's history. The accident marked the 767's first fatal incident and third [[hull loss]].<ref name="ASN">{{ASN accident|id=19910526-0}}.</ref><ref>{{Cite web |last=Ranter |first=Harro |title=Boeing 767 |url=https://aviation-safety.net/database/types/Boeing-767/index |access-date=2019-03-06 |website=Aviation Safety Network |publisher=Flight Safety Foundation}}</ref><ref>{{Cite web |last=Ranter |first=Harro |title=Thailand air safety profile |url=http://aviation-safety.net/database/country/country.php?id=HS |access-date=2019-03-06 |website=Aviation Safety Network |publisher=Flight Safety Foundation}}</ref> [[Formula One]] world motor racing champion [[Niki Lauda]], who founded and ran [[Lauda Air]], was personally involved in the accident investigation.

==Aircraft==
The aircraft involved was a Boeing 767-300ER, the 283rd Boeing 767 built,<ref name="report" /> that was powered by [[Pratt & Whitney PW4000|Pratt & Whitney PW4060]] engines and was delivered new to Lauda Air on 16 October 1989.{{cn|date=November 2025}} The aircraft was registered OE-LAV and named ''[[Wolfgang Amadeus Mozart|Mozart]]''.<ref name="report">{{cite web|url=http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/ComAndRep/LaudaAir/LaudaRPT.html|title=Accident Report|website=rvs.uni-bielefeld.de|publisher=Aircraft Accident Investigation Committee|url-status=dead|archive-url=https://web.archive.org/web/20110607000248/http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/ComAndRep/LaudaAir/LaudaRPT.html|archive-date=7 June 2011|access-date=14 February 2014}}</ref>{{Rp|21}} At the time of the incident, the [[Aircraft engine#Engine position numbering|No. 2 engine]] had been on the airframe since assembly of the aircraft (7,444 hours and 1,133 cycles) whereas the [[Aircraft engine#Engine position numbering|No. 1 engine]] (with the faulty thrust reverser) had been on the aircraft since October 3, 1990 and had accumulated 2,904 hours and 456 cycles.<ref name="report"/>{{Rp|4}}

==Accident==
At the time of the accident, [[Lauda Air]] operated three weekly flights between [[Bangkok]] and [[Vienna]].<ref name="Causesought2">{{Cite news |last=Tummachartvijit |first=Tavorn |date=27 May 1991 |title=Cause of airliner explosion Sought |url=https://news.google.com/newspapers?id=zTkeAAAAIBAJ&sjid=074EAAAAIBAJ&pg=4885,3881244&dq=lauda+air+crash+passenger+list&hl=en |access-date= |work=[[The Dispatch (Lexington)|The Dispatch]] |pages=1A and 6A |via=Google News |agency=[[Associated Press]]}}</ref> At 23:02 [[Time in Thailand|ICT]] on 26 May 1991, the [[Boeing 767|Boeing 767-3Z9ER]] operating as Flight&nbsp;4 (originating from Hong Kong's [[Kai Tak Airport]]) departed [[Don Mueang International Airport]] in Bangkok for its passenger service to [[Vienna International Airport]] with 213 passengers and 10 crew under the command of American captain Thomas John Welch<!--Full name from http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/ComAndRep/LaudaAir/LaudaRPT.html--> (48) and Austrian first officer Josef Thurner (41).<ref name="report" />{{Rp|4}}<ref>{{Cite news |title=Excerpts from Lauda News Conference on Crash of Boeing 767 With AM-Thailand Crash |work=AP NEWS |agency=Associated Press |url=https://apnews.com/5ae6ab328db1fa2c8374f267c20c5cd3 |date=1991-06-02|access-date=2020-05-25|archive-url=https://web.archive.org/web/20221210024015/https://apnews.com/article/5ae6ab328db1fa2c8374f267c20c5cd3|archive-date=2022-12-10}}</ref><ref>{{Cite book |last=Lewis Jr. |first=Joseph W. |url=https://books.google.com/books?id=s8xwDQAAQBAJ&q=First+Officer+Josef+Thurner&pg=PT644 |title=Last and Near-Last Words of the Famous, Infamous and Those In-Between |date=2016-10-28 |publisher=AuthorHouse |isbn=978-1-5246-4787-2 |language=en}}</ref><ref name="Partners">{{Cite news |title=Two Doomed 767S Were Partners On Assembly Line |url=https://archive.seattletimes.com/archive/?date=19991101&slug=2992564 |work=The Seattle Times |access-date=2020-05-25}}</ref><ref>{{Cite web |title=Lauda 004 air crash |url=http://www.pilotfriend.com/disasters/crash/lauda004.htm |website=Pilotfriend |access-date=2020-05-25}}</ref><ref name="tailstrike.com">{{Cite web |title=Lauda Air 004 CVR Transcript |url=https://www.tailstrike.com/260591.htm |website=Cockpit Voice Recorder Database |access-date=2020-05-25}}</ref> Both pilots were regarded as very competent. At 23:08, Welch and Thurner received a visual warning indication on the [[Engine-indicating and crew-alerting system|EICAS]] display that a possible system failure would cause the thrust reverser on the No.&nbsp;1 engine to deploy in flight. After consulting the aircraft's [[Quick Reference Handbook]], they determined that the alert was "coming on and off" and that it was "just an advisory thing". The pilots took no remedial action, possibly believing that the indication was false, but also with the knowledge that the 767 could land safely with only one operational reverser.<ref name="ASN" />

At 23:17, the No. 1 engine reverser deployed while the plane was over mountainous jungle terrain in the border area between the [[Suphan Buri province|Suphan Buri]] and [[Uthai Thani province|Uthai Thani]] provinces in Thailand. Thurner's last recorded words were "Oh, reverser's deployed."<ref name="Air Disaster Volume 2">{{Cite book |last=Job |first=Macarthur |author-link=Macarthur Job |title=Air Disaster Volume 2 |publisher=Aerospace Publications |year=1996 |isbn=1-875671-19-6 |pages=203–217}}</ref><ref name="report"/>{{Rp|55}} Moments later, the cockpit voice recorder (CVR) recorded a shuddering sound, followed closely by a snap. Due to the reverser design, an aerodynamic plume of air disrupted the airflow over the [[leading edge]] of the left wing during the engine's rundown to idle thrust, which resulted in a 25% loss of lift and an [[Stall (fluid dynamics)|aerodynamic stall]].

The aircraft immediately began a diving left turn. The CVR recorded master caution warning and a second snapping sound, followed by various alerts such as [[V speeds|overspeed]] and a second master caution, and Welch's last recorded words: "Jesus Christ" in response to the rapid rolling sensation, "here, wait a minute" as he brought engine 1's thrust lever to idle and shut down the engine and finally, "damn it". Following this, the CVR recorded an increase in background wind noise followed by several loud bangs. Maneuvering overloads produced by the pilots' sustained attempts to regain pitch control, in combination with the increasing velocity of the dive, had exceeded the aircraft's structural limits and destroyed the weakened aft fuselage along with the rest of the damaged flight surfaces. The loss of the tail caused further negative loading of the wings, as the airplane experienced [[Mach tuck]] and nosed over vertically, reaching a speed of at least [[Mach number|Mach]]&nbsp;0.99 (the highest value that the aircraft's sensors could record), breaking the [[sound barrier]].

The wings then experienced [[Structural integrity and failure|structural failure]] and separated at the trailing edges, engulfing the remains of the falling aircraft in flames before impacting mountainous wooded terrain and exploding.<ref>{{Cite book |last=Chiles |first=James R. |url=https://books.google.com/books?id=HY2VzalG_7cC&dq=%22Lauda+Air+767+airliner%22&pg=PA309 |title=Inviting Disaster: Lessons From the Edge of Technology: An Inside Look at Catastrophes and Why They Happen |date=2008-07-08 |publisher=Harper Collins |isbn=978-0-06-173458-8 |pages=309}}</ref> Most of the wreckage was scattered over a remote forest area roughly {{convert|1|sqkm|sqmi}} in size, at an elevation of {{convert|600|m|abbr=on}}, in what is now [[Phu Toei National Park]], Suphan Buri. The wreckage site is about {{convert|6|km|mi nmi|0|abbr=}} north-northeast of [[Phu Toey]], [[Huay Kamin]] ({{langx|th|ห้วยขมิ้น}}), [[Dan Chang district]], [[Suphan Buri province]],<ref name="report"/> about {{convert|100|km|mi nmi|abbr=}} northwest of [[Bangkok]], close to the Burma-Thailand border.<ref name="Causesought2"/><ref name="Morethan200">{{Cite news |last= |first= |date=27 May 1991 |title=More Than 200 Believed Killed As Plane Crashes in Thai Jungle |url=https://www.nytimes.com/1991/05/27/world/more-than-200-believed-killed-as-plane-crashes-in-thai-jungle.html |access-date=27 January 2013 |work=The New York Times |issn=0362-4331 |agency=Associated Press}}</ref> Rescuers found Welch's body still in the pilot's seat.<ref name="Independent1991UNdrugman">{{Cite news |date=30 May 1991 |title=UN drug man 'not Thai bomb target' |work=[[The Independent]]}} Available on [[LexisNexis]].</ref>

==Recovery==
Volunteer rescue teams and local villagers looted the wreckage, taking electronics and jewellery,<ref>{{Cite news |last=Johnson |first=Sharen Shaw |date=29 May 1991 |title=Scavengers complicate crash probe |newspaper=USA Today |page=[https://www.newspapers.com/article/usa-today-for-lauda-air-flight-004/175595260/ 4A]|via=[[Newspapers.com]]}}</ref> so relatives were unable to recover personal possessions.<ref>{{cite news |last1=Krausz |first1=Tibor |title=Pilgrimage to Thai plane crash site for aunt killed 28 years ago: 'I'm here for you. You're no longer alone.' |url=https://www.scmp.com/lifestyle/travel-leisure/article/3041245/pilgrimage-thai-plane-crash-site-aunt-killed-28-years-ago |access-date=10 December 2019 |work=South China Morning Post |date=10 December 2019}}</ref> The bodies were taken to a hospital in Bangkok, but the storage was not refrigerated, and the bodies decomposed. Dental and forensic experts worked to identify bodies, but 27 were never identified.<ref name="Finlayanniv">{{Cite news |last=Finlay |first=Victoria |date=25 May 1993 |title=Relatives return to crash site for memorial service |url=https://www.scmp.com/article/30842/relatives-return-crash-site-memorial-service |access-date=26 May 2013 |newspaper=South China Morning Post}}</ref>

Speculation circulated that a bomb may have destroyed the aircraft, as some eyewitnesses had reported seeing a large fireball surrounding the aircraft, the result of the disintegration of the right wing during the dive. However, a terrorist motive was believed unlikely, as Austria was politically neutral with a reputation of avoiding international conflicts such as the recent [[Gulf War]].<ref name="Looting1">{{Cite news |date=29 May 1991 |title=Looting May Hurt Jet-crash Probe; Airline Chief Denies Extortion Plot |url=http://articles.philly.com/1991-05-29/news/25796133_1_austrian-airliner-lauda-air-boeing-extortion-plot |url-status=dead |archive-url=https://web.archive.org/web/20140416192325/http://articles.philly.com/1991-05-29/news/25796133_1_austrian-airliner-lauda-air-boeing-extortion-plot |archive-date=16 April 2014 |access-date=26 May 2013 |newspaper=[[The Philadelphia Inquirer]] |pages=1 |via=Inquirer Wire Services}}</ref>

== Investigation ==
[[File:Lauda Frankfurt 1996 crop.JPG|thumb|[[Niki Lauda]] travelled to Thailand to assist in the investigation.]]
The [[Flight recorder#Flight data recorder|flight data recorder]] was completely destroyed, so only the [[Flight recorder#Cockpit voice recorder|cockpit voice recorder]] could be analysed. Thailand's Air Safety Division head Pradit Hoprasatsuk stated that "the attempt to determine why the reverser came on was hampered by the loss of the flight data recorder, which was destroyed in the crash".<ref>{{Cite news |date=31 August 1993 |title=Probe Fails to Resolve Cause of 1991 Air Disaster |url=http://www.apnewsarchive.com/1993/Probe-Fails-to-Resolve-Cause-of-1991-Air-Disaster/id-215788658f0d9a3e1949c3f4092dd913 |url-status=dead |archive-url=https://web.archive.org/web/20140316111147/http://www.apnewsarchive.com/1993/Probe-Fails-to-Resolve-Cause-of-1991-Air-Disaster/id-215788658f0d9a3e1949c3f4092dd913 |archive-date=16 March 2014 |access-date=16 March 2014 |agency=Associated Press}}</ref> Upon hearing of the crash, Niki Lauda traveled to Thailand. He examined the wreckage and estimated that the largest fragment was about {{convert|5|m|ft|spell=in}} by {{convert|2|m|ft|spell=in}}, which was about half the size of the largest piece resulting from the [[Pan Am Flight 103|Lockerbie bombing]].<ref>{{Cite news |date=30 May 1991 |title=Looting may have hidden clues to crash |work=[[The Advertiser (Adelaide)|The Advertiser]]}}</ref> Lauda attended a funeral for 23 unidentified passengers in Thailand and then traveled to [[Seattle]] to meet with [[Boeing]] representatives.

The official investigation, led by Thailand's [[Aircraft Accident Investigation Committee]], lasted approximately eight months and resulted in a conclusion of probable cause: "The Accident Investigation Committee of the Government of Thailand determines the probable cause of this accident to be [an] uncommanded in-flight deployment of the left engine thrust reverser, which resulted in loss of flight path control. The specific cause of the thrust reverser deployment has not been positively identified."<ref name="LaudaGuardian">{{Cite news |last1=Lauda |first1=Nicki |last2=Hamilton |first2=Maurice |date=29 October 2006 |title=Niki Lauda: 'People had lost their loved ones yet no one was telling them why' |url=https://www.theguardian.com/sport/2006/oct/29/features.sportmonthly |access-date=15 February 2013 |work=[[The Observer]] |issn=0029-7712}}</ref> Multiple possibilities were investigated, including a short circuit in the electrical system. However, the destruction of much of the wiring meant that investigators could not arrive at a definitive reason for the activation of the thrust reverser.<ref name="report"/>

As evidence began to implicate the thrust reversers as the cause of the accident, Lauda conducted simulator flights at [[Gatwick Airport]] that appeared to show that deployment of a thrust reverser was a survivable condition. Lauda said that the thrust reverser could not be the sole cause of the crash.<ref name="nyt rejects">{{Cite news |date=7 June 1991 |title=Owner Rejects Thrust as Cause of Air Crash |url=https://www.nytimes.com/1991/06/07/world/owner-rejects-thrust-as-cause-of-air-crash.html |access-date=26 January 2013 |work=The New York Times |issn=0362-4331}}</ref> However, the accident report states that the "flight crew training simulators yielded erroneous results"<ref name="report"/>{{Rp|21}} and that recovery from the loss of lift from the reverser deployment "was uncontrollable for an unexpecting flight crew".<ref name="report"/>{{Rp|41}}

The incident prompted Boeing to modify the thrust-reverser system to prevent similar occurrences by adding sync locks, which prevent the thrust reversers from deploying when the main [[Landing gear|landing-gear]] truck-tilt angle is not at the ground position.<ref  name="report"/><ref>{{cite news |author=Acohido, Byron |date=3 November 1999 |title=Boeing Thrust Reversers Had History Of Glitches |url=https://www.chicagotribune.com/1999/11/03/boeing-thrust-reversers-had-history-of-glitches/ |work=Chicago Tribune}}</ref> Aviation writer [[Macarthur Job]] has stated that "had that Boeing&nbsp;767 been of an earlier version of the type, fitted with engines that were controlled mechanically rather than electronically, then that accident could not have happened".<ref name= "Air Disaster Volume 2"/>

=== Lauda's visit with Boeing ===
Lauda stated: "What really annoyed me was Boeing's reaction once the cause was clear. Boeing did not want to say anything."<ref name=LaudaGuardian/> He asked Boeing to fly the scenario in a simulator using data different from that which Lauda had employed in his tests at Gatwick Airport.<ref name="Air Crash Investigations: Suddenly Falling Apart The Crash Of Lauda Air Flight NG 004">{{Cite book |last=Williamson |first=Hank |url=https://books.google.com/books?id=XHssAwAAQBAJ |title=Air Crash Investigations: Suddenly Falling Apart the Crash of Lauda Air Flight Ng 004 |date=2011-05-01 |publisher=Lulu.com |isbn=978-1-257-50540-1 |pages=40}}</ref> Boeing initially refused, but Lauda insisted, so Boeing granted permission. Lauda attempted the flight in the simulator 15 times, and in every instance, he was unable to recover. He asked Boeing to issue a statement, but the company's legal department replied that it would take three months to adjust the wording. Lauda asked for a press conference the following day and told Boeing that if it was possible to recover, he would be willing to fly a 767 with two pilots and have the thrust reverser deploy in air. Boeing told Lauda that it was not possible, so he persuaded Boeing to issue a statement saying that such a scenario would not be survivable. Lauda then added that "this was the first time in eight months that it had been made clear that the manufacturer [Boeing] was at fault and not the operator of the aeroplane [or Pratt and Whitney]".<ref name=LaudaGuardian/>

=== Previous testing of thrust reversers ===
When the U.S. [[Federal Aviation Administration]] (FAA) asked Boeing to test activating the thrust reverser in flight,<ref>{{Cite book |last=Chiles |first=James R. |url=https://books.google.com/books?id=HY2VzalG_7cC&pg=PA112 |title=Inviting Disaster: Lessons From the Edge of Technology: An Inside Look at Catastrophes and Why They Happen |date=2008-07-08 |publisher=Harper Collins |isbn=978-0-06-173458-8 |pages=112–113}}</ref> the FAA had allowed Boeing to devise the tests. Boeing had insisted that a deployment was not possible in flight. In 1982, Boeing conducted a test in which the aircraft was flown at {{convert|10,000|ft|m}}, slowed to {{convert|250|kn|km/h mph m/s}}, and then the test pilots deployed the thrust reverser. The control of the aircraft was not jeopardized, and the FAA accepted the results of the test.<ref>{{Cite book |last=Chiles |first=James R. |url=https://books.google.com/books?id=HY2VzalG_7cC&pg=PA113 |title=Inviting Disaster: Lessons From the Edge of Technology: An Inside Look at Catastrophes and Why They Happen |date=2008-07-08 |publisher=Harper Collins |isbn=978-0-06-173458-8 |pages=113}}</ref>

The Lauda aircraft was travelling at a [[True airspeed|TAS]] <!-- Delete "speed" (redundant) --> of {{convert|400|kn|km/h mph}} at {{convert|24700|ft|m}} in the climb to {{convert|30000|ft|m}}<ref>"[http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/ComAndRep/LaudaAir/LaudaRPT.html Lauda Air B767 Accident Report]", 26 May 1991.</ref> when the left thrust reverser deployed, causing the pilots to lose control of the aircraft. James R.&nbsp;Chiles, author of ''Inviting Disaster'', said: "[T]he point here is not that a thorough test would have told the pilots Thomas J.&nbsp;Welch and Josef Thurner what to do. A thrust reverser deploying in flight might not have been survivable, anyway. But a thorough test would have informed the FAA and Boeing that thrust reversers deploying in midair was such a dangerous occurrence that Boeing needed to install a positive lock that would prevent such an event."<ref>{{Cite book |last=Chiles |first=James R. |url=https://books.google.com/books?id=HY2VzalG_7cC&pg=PA114 |title=Inviting Disaster: Lessons From the Edge of Technology: An Inside Look at Catastrophes and Why They Happen |date=2008-07-08 |publisher=Harper Collins |isbn=978-0-06-173458-8 |pages=114}}</ref>

==Passengers and crew==
{| class="sortable wikitable" style="font-size:85%; margin:0 0 0.5em 1em; float:right;"
!Nation!!Passengers!!Crew!!Total
|-<!-- Country links unnecessary. See [[MOS:OVERLINK]]. -->
|Austria||74||9||83
|-
|Hong Kong||52||0||52
|-
|Thailand||39||0||39
|-
|Italy||10||0||10
|-
|Switzerland||7||0||7
|-
|China||6||0||6
|-
|Germany||4||0||4
|-
|Portugal||3||0||3
|-
|Taiwan||3||0||3
|-
|Yugoslavia||3||0||3
|-
|United States||2||1{{efn|The captain.}}||3
|-
|Hungary||2||0||2
|-
|Philippines||2||0||2
|-
|United Kingdom||2||0||2
|-
|Australia||1||0||1
|-
|Brazil||1||0||1
|-
|Poland||1||0||1
|-
|Turkey||1||0||1
|-
!'''Total'''||'''213'''||'''10'''||'''223'''
|}

The passengers and crew included 83 Austrians: 74 passengers and 9 crew members.<ref name="TraynorIndependentplaneblast">{{Cite news |last=Traynor |display-authors=et al |date=28 May 1991 |title=Crash teams investigate plane blast |work=The Independent}}</ref><ref name="Wallace2">{{Cite news |last=Wallace |first=Charles P. |date=28 May 1991 |title='All Evidence' in Thai Air Crash Points to Bomb |url=https://www.latimes.com/archives/la-xpm-1991-05-28-mn-2556-story.html |access-date=15 February 2013 |work=Los Angeles Times |pages=2}}</ref> Other nationalities included 52 Hong Kong residents,<ref name=Wallace2/><ref name="Finlaywait">{{Cite news |last=Finlay |first=Victoria |date=25 May 1993 |title=Jet tragedy families wait on pay |url=https://www.scmp.com/article/30841/jet-tragedy-families-wait-pay |access-date=27 January 2013 |work=South China Morning Post}}</ref> 39 Thai, 10 Italians, 7 Swiss, 6 Chinese, 4 Germans, 3 Portuguese, 3 Taiwanese, 3 Yugoslavs, 2 Hungarians, 2 Filipinos, 2 Britons, 3 Americans (two passengers and the captain), 1 Australian, 1 Brazilian, 1 Pole and 1 Turk.<ref name=Wallace2/><ref name="Finalwords">{{Cite news |date=6 June 1991 |title=Pilot's Final Words |url=https://archive.seattletimes.com/archive/19910606/1287449/pilots-final-words |url-status=live |archive-url=https://web.archive.org/web/20140729033714/http://community.seattletimes.nwsource.com/archive/?date=19910606&slug=1287449 |archive-date=29 July 2014 |access-date=15 February 2013 |work=The Seattle Times |agency=Associated Press}}</ref>

First officer Josef Thurner had once flown as a copilot with Niki Lauda on a Lauda Air Boeing 767 service to Bangkok, a flight that was the subject of a ''[[Reader's Digest]]'' article in January 1990 that depicted the airline positively. [[Macarthur Job]] stated that Thurner was the better known of the crew members.<ref>Job, p. 204. "Of all the crew, Josef Thurner was perhaps the better known thanks to having been copilot to Niki Lauda himself on a Boeing 737 service to Bangkok which became the subject of a highly affirmative article on the airline and its history in the January 1990 issue of ''[[Reader's Digest]]''&nbsp;[...]"</ref> Captain Thomas J.&nbsp;Welch lived in [[Vienna]]<ref name=Wallace2/> but was originally from [[Seattle]], Washington.<ref name=Finalwords/>

Notable victims included:
* [[Clemens August Andreae]], an Austrian economics professor,<ref name="DiePresseUngluck">{{Cite news |last= |first= |date=26 May 2011 |title=Lauda Air-Absturz in Thailand jährt sich zum 20. Mal |trans-title=Lauda Air Crash in Thailand marks its 20th anniversary |url=https://www.diepresse.com/665068/lauda-air-absturz-in-thailand-jaehrt-sich-zum-20-mal |access-date=14 February 2013 |work=[[Die Presse]] |language=de}}</ref> was leading a group of students from the [[University of Innsbruck]] on a tour of the Far East.<ref name="ParschalkThaler394">{{Cite book |last=Thaler |first=Bernhard |url=https://books.google.com/books?id=eqYtAQAAIAAJ&q=Andreae+ |title=Südtirol Chronik: das 20. Jahrhundert |date=1999 |publisher=Athesia |isbn=978-88-8266-016-1 |page=394 |language=de |trans-title=South Tyrol Chronicle: the 20th century |quote=Sechs der zehn Südtiroler Opfer sind Studenten der Innsbrucker Fakultät für Wirtschaftswissenschaften aus Klausen, Gröden, Olang, Mals und Kiens, die unter der Leitung von Clemens August Andreae an einer Exkursion nach Fernost teilgenommen hatten. Die anderen vier Südtiroler Todesopfer – alle aus Bozen – sind zwei Beamte sowie ein Berufsmusiker mit seiner chinesischen Frau und dem in Bozen geborenen Töchterchen der beiden. [English: Six of the ten victims of South Tyrol are students of the Innsbruck Faculty of Economics from Klausen, Val Gardena, Olang, Mals and Kiens, who had participated in an excursion to the Far East under the guidance of Clemens August Andreae. The other four South Tyrolean fatalities – all from Bolzano – are two civil servants and a professional musician with his Chinese wife and the Bolzano-born daughter of the two. }}</ref>
* [[Pairat Decharin]], the governor of [[Chiang Mai province]], and his wife.<ref name="Independent1991UNdrugman"/><ref>{{cite web |url=http://www.chiangmai.go.th/newweb/data/governor_list.php |work=Chiang Mai Province Official Site |language=th |script-title=th:รายนามผู้ดำรงตำแหน่งผู้ว่าราชการจังหวัดเชียงใหม่ |trans-title=List of incumbent governor of Chiang Mai Province |access-date=17 March 2017}}</ref> Charles S.&nbsp;Ahlgren, the former U.S. consul general to [[Chiang Mai]], said: "That accident not only took their lives and that of many of Chiang Mai's leaders, but dealt a blow to many development and planning activities in the town."<ref>"[https://photos.state.gov/libraries/chiangmai/231771/PDFs/60th%20anniversary%20presentation%2001-20-11%20EN.pdf Special Messages from 8 U.S. Consuls General in Chiang Mai]". ([https://web.archive.org/web/20140811095048/http://photos.state.gov/libraries/chiangmai/231771/PDFs/60th%20anniversary%20presentation%2001-20-11%20EN.pdf Archive]) [[United States Department of State]]. Retrieved on 15 February 2013. [https://photos.state.gov/libraries/chiangmai/231771/PDFs/60th%20anniversary%20presentation%2001-20-11%20TH.pdf Thai version], [https://web.archive.org/web/20140811095258/http://photos.state.gov/libraries/chiangmai/231771/PDFs/60th%20anniversary%20presentation%2001-20-11%20TH.pdf Archive].</ref>
* Princess {{ill|Phongkaeo of Chiang Mai|th|เจ้าพงศ์แก้ว ณ ลำพูน}} ([[Chet Ton dynasty]]).

==Aftermath==
[[File:Lauda cemetery.jpg|thumb|Flight 004 Memorial near Suphanburi]]
About a quarter of the airline's carrying capacity was destroyed as a result of the crash.<ref>Traynor, Ian. "Lauda's driving ambition brings triumph and disaster in tandem". ''[[The Independent]]''. 28 May 1991.</ref> Following the crash of OE-LAV, the airline operated no flights to [[Sydney]] on 1, 6 and 7 June. Flights resumed with another 767 on 13 June.<ref>{{Cite book |url=https://books.google.com/books?id=Ql4pAQAAIAAJ&q=%22OE-LAV%22+Lauda |title=Aircraft & Aerospace |date=1991 |publisher=Peter Isaacson Publications Pty. Limited |pages=44 |quote=LAUDA AIR/LDA: Following the still unexplained loss of B767-329ER OE-LAV [24628] Mozart, there were no flights to Sydney by the Austrian carrier on 1, 6 and 7 June. Services resumed on 13 June with B767-3T9 (ER) OE-LAU [23765 xN6009F]}}</ref> Niki Lauda said that the crash and the ensuing period constituted the worst time in his life, even worse than the recovery from injuries that he had sustained after a crash in the [[1976 German Grand Prix]].<ref name=LaudaGuardian/> After the Flight 004 crash, bookings from Hong Kong decreased by 20%, but this was offset by an increase in bookings by passengers based in Vienna.<ref name=Finlaywait/>

In early August 1991, Boeing issued an alert to airlines stating that more than 1,600 late-model 737s, 747s, 757s and 767s had thrust-reverser systems similar to that of OE-LAV. Two months later, customers were asked to replace potentially faulty valves in the thrust-reverser systems that could cause reversers to deploy in flight.<ref>{{Cite news |last1=Lane |first1=Polly |last2=Acohido |first2=Byron |date=9 September 1991 |title=Boeing Tells 757 Owners To Replace Part – Faulty Thrust-Reverser Valve Blamed In 767 Accident That Killed 223 |url=https://archive.seattletimes.com/archive/?date=19910909&slug=1304510 |access-date=15 February 2013 |work=[[The Seattle Times]]}}</ref>

At the crash site, which is accessible to national park visitors, a shrine was erected to commemorate the victims.<ref>{{Cite web |date=19 January 2007 |title=Truly Unseen: Phu Toei National Park |url=http://www.thai-blogs.com/2007/01/19/truly-unseen-phutoei-national-park/ |url-status=usurped |archiveurl=https://web.archive.org/web/20101208093348/http://www.thai-blogs.com/2007/01/19/truly-unseen-phutoei-national-park/ |archivedate=8 December 2010 |website=Thai Blogs}}</ref> Another memorial and cemetery is located at [[Wat Sa Kaeo Srisanpetch]], about {{convert|90|km|mi nmi|abbr=}} away in [[Mueang Suphan Buri district]].<ref>{{Cite web |date=22 September 2009 |title=Lauda Air Crash, 26 May 1991: Thailand's Worst Ever |url=http://www.thai-blogs.com/2009/09/22/lauda-air-crash-26-may-1991-thailand-s-w/ |archive-url=https://web.archive.org/web/20101215184701/http://www.thai-blogs.com/2009/09/22/lauda-air-crash-26-may-1991-thailand-s-w/ |url-status=usurped |archive-date=15 December 2010 |access-date=2019-09-29 |website=Thai Blogs}}</ref>

==In popular culture==
The crash of Flight 004 was featured in an edition of ITV's [[The Cook Report]] entitled "Don't Shoot the Pilot" in 1993 and in the second episode of Season 14 of the Canadian documentary television series ''[[Mayday (Canadian TV series)|Mayday]]'', titled "Testing the Limits".<ref>{{cite web |title=Niki Lauda: Testing the Limits (Lauda Air Flight 004) |url=https://thetvdb.com/series/mayday/episodes/4981724 |website=TheTVDB.com |access-date=3 March 2022}}</ref>

==See also==
{{Portalbar|Austria|Thailand|Aviation|Modern history|1990s}}
* [[TAM Airlines Flight 402]], another accident caused by an uncommanded reverse thruster deployment. Coincidentally, it is also the deadliest accident involving the aircraft family involved.
* [[Pacific Western Airlines Flight 314]]

== Notes ==
{{notelist}}

==References==
{{Reflist|30em}}

==Citations==
* [http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/ComAndRep/LaudaAir/LaudaRPT.html Accident Report — Lauda Air Flight 004] ([https://web.archive.org/web/20110607000248/http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/ComAndRep/LaudaAir/LaudaRPT.html Archive]) — [[Aircraft Accident Investigation Committee]], [[Ministry of Transport (Thailand)|Ministry of Transport and Communications Thailand]], Prepared for [[World Wide Web]] usage by Hiroshi Sogame (十亀 洋 ''Sogame Hiroshi''), a member of the Safety Promotion Committee (総合安全推進 ''Sōgō Anzen Suishin'') of [[All Nippon Airways]]
* ''Aircraft, Volume 71''. [[Royal Aeronautical Society]] Australian Division, 1991.
* Chiles, James R. ''Inviting Disaster''. [[HarperCollins]], 8 July 2008. {{ISBN|0061734586}}, 9780061734588.
* [[Macarthur Job|Job, Macarthur]]. ''Air Disaster, Volume 2''. Aerospace Publications, 1996. {{ISBN|1875671196}}, 9781875671199.
* Parschalk, Norbert and Bernhard Thaler. ''Südtirol Chronik: das 20. Jahrhundert''. Athesia, 1999.

==Further reading==
* Gilbert, Andy. "[https://www.scmp.com/article/75527/lauda-air Lauda Air]". ''[[South China Morning Post]]''. Thursday 26 May 1994.
* ''[[Aviation Week & Space Technology]]''. 1991-10-03 (32), 1991-10-06 (28–30)
* {{cite web|last=Hamilton|first=Maurice|url=https://theroadrat.com:443/a/downloads/-/bb18383dde3431a7/8584b9f7b45b3512/download|title=Flight & Fight|magazine=The Ratchet|publisher=[[Guy Berryman|The Road Rat]]|issue=7}} - Includes interview content with Niki Lauda, from an excerpt of a book by Maurice Hamilton ([https://theroadrat.com/pages/the-ratchet profile of the magazine])

==External links==
{{Commons category|Lauda Air Flight 004}}
*[http://www.austrianwings.info/2015/01/lauda-air-crash-1991-still-too-many-open-questions/ Lauda Air Crash 1991: still too many open questions]&nbsp;—  Austrian Wings&nbsp;—  Austrias Aviation Magazine
*"[http://www.aviation.go.th/rbm/accident%20Investigate.pdf การสอบสวนอากาศยานประสบอุบัติเหต]" [[Department of Civil Aviation (Thailand)|Department of Civil Aviation]] {{in lang|th}} ([https://web.archive.org/web/20120311091151/http://www.aviation.go.th/rbm/accident%20Investigate.pdf Archive])
*[http://www.rvs.uni-bielefeld.de/publications/Incidents/DOCS/ComAndRep/LaudaAir/LaudaRPT.html "Lauda Air B767 accident report"] Ministry of Transport & Communications Thailand (in English)
*"[http://www.rvs.uni-bielefeld.de/publications/compendium/incidents_and_accidents/lauda_air_b767.html Computer-Related Incidents with Commercial Aircraft The Lauda Air B767 Accident]". ([https://web.archive.org/web/20140327234142/http://www.rvs.uni-bielefeld.de/publications/compendium/incidents_and_accidents/lauda_air_b767.html Archive]) [[Bielefeld University]]. 26 May 1991.
*[http://www.scmp.com/topics/lauda-air-flight-004 Lauda Air Flight 004] (Index of articles)&nbsp;—  ''[[South China Morning Post]]''
*"[http://www.uibk.ac.at/ipoint/traueranzeigen/2011/flugzeugabsturz_20jahre.pdf flugzeugabsturz_20jahre.pdf]" ([https://web.archive.org/web/20111223124912/http://www.uibk.ac.at/ipoint/traueranzeigen/2011/flugzeugabsturz_20jahre.pdf Archive]) [[University of Innsbruck]].&nbsp;— Includes list of University of Innsbruck professors, assistants, and students who died on Flight 004
*[http://www.austrianwings.info/aw/?p=26533 Last flight of the Mozart (Der Todesflug der Mozart, German)]&nbsp;—  ''Austrian Wings''&nbsp;—  Austria's Aviation Magazine
*[http://www.planecrashinfo.com/1991/1991-27.htm PlaneCrashInfo.com&nbsp;—  Lauda Air Flight 004]
*[https://tailstrike.com/database/26-may-1991-lauda-air-004/ Cockpit Voice Recorder transcript and accident summary]
*[http://www.grandprixhistory.org/lauda_bio.htm Grand Prix History&nbsp;—  Biography on Niki Lauda (Contains information about Flight 004)]
{{Niki Lauda}}{{Aviation accidents and incidents in Thailand}}
{{Aviation accidents and incidents in 1991}}

[[Category:Airliner accidents and incidents caused by mechanical failure]]
[[Category:Aviation accidents and incidents in 1991]]
[[Category:Aviation accidents and incidents in Thailand]]
[[Category:Accidents and incidents involving the Boeing 767]]
[[Category:1991 in Thailand]]
[[Category:Lauda Air accidents and incidents]]
[[Category:Austria–Thailand relations]]
[[Category:May 1991 in Thailand]]
[[Category:Niki Lauda]]
[[Category:Airliner accidents and incidents caused by design or manufacturing errors]]