View source for Flight level

{{Short description|Measure in aviation}}
{{Use dmy dates|date=September 2019}}
{{Multiple issues|
{{More citations needed
| date = December 2016}}
{{technical|date=January 2023}}
{{Outdated as of | topic = usage of metric flight levels in Kyrgyzstan, Kazakhstan, Tajikistan, Uzbekistan, and Turkmenistan | last updated = | year = 2024 | month = 12 | day = 16 }}
}}
In [[aviation]], a '''flight level''' ('''FL''') is an aircraft's [[altitude]] as determined by a pressure altimeter using the [[International Standard Atmosphere]]. It is expressed in hundreds of [[foot (unit)|feet]] or [[metres]]. The altimeter setting used is the [[International Standard Atmosphere|ISA]] sea level pressure of 1013&nbsp;[[Pascal (unit)|hPa]] or 29.92&nbsp;[[Inch of mercury|inHg]]. The actual surface pressure will vary from this at different locations and times. Therefore, by using a standard pressure setting, every aircraft has the same altimeter setting, and vertical clearance can be maintained during cruise flight.<ref>{{cite book |title=A Dictionary of Aviation |first=David W. |last=Wragg |isbn=9780850451634 |edition=first |publisher=Osprey |year=1973 |page=133}}</ref>
[[File:comparison_flight_levels.svg|thumb|upright=1.5|Scale comparison of some flight level systems]]

==Background==
Flight levels are used to ensure safe vertical separation between aircraft. Historically, altitude has been measured using an  [[altimeter]], essentially a calibrated [[barometer]]. An altimeter measures ambient air pressure, which decreases with increasing altitude following the [[barometric formula]]. It displays the corresponding altitude. If aircraft altimeters were not calibrated consistently, then two aircraft could be flying at the same altitude even though their altimeters appeared to show that they are at different altitudes.<ref>See also [http://www.skybrary.aero/index.php/Level_Bust Level Bust] for related causes and consequences</ref> Flight levels require defining altitudes based on a standard altimeter setting. All aircraft operating at flight levels set 1013&nbsp;hPa or 29.92&nbsp;inHg. On the descent when descending through the published transition level, the altimeter is set to the local surface pressure, to display the correct altitude above sea level.

== Definition ==
Flight levels<ref>{{cite book |url=https://www.faa.gov/air_traffic/publications/media/pcg_basic_chgs%201_2_9-13-18.pdf |title=Aeronautical Information Manual |author=Federal Aviation Administration |author-link=Federal Aviation Administration |chapter=Pilot/Controller Glossary |page=PCG F−3 |date= 29 March 2018 |access-date=1 March 2019}}</ref> are described by a number, which is the nominal altitude, or [[pressure altitude]], in hundreds of feet, and a multiple of 100&nbsp;ft. Therefore, a pressure altitude of {{cvt|32000|ft}} is referred to as "flight level 320". In metre altitudes the format is xx000 metres.

Flight levels are usually designated in writing as ''FLxxx'', where ''xxx'' is a two- or three-digit number indicating the pressure altitude in units of {{convert|100|ft|m}}. In radio communications, FL290 would be stated as "flight level two nine(r) zero".

==Transition altitude==
While use of a standardised pressure setting facilitates separation of aircraft from each other, it does not provide the aircraft's actual altitude above sea level. Below the Transition level (which varies worldwide), the altimeter is set to the local altimeter setting, which can be directly compared to the known [[elevation]] of the terrain. The pressure setting to achieve this varies with local atmospheric pressure. It is called [[QNH]] ("barometric pressure adjusted to sea level"), or "[[altimeter setting]]", the current local value is available from various sources, including [[air traffic control]] and the local airport weather frequency or a [[METAR]]-issuing station.

The '''transition altitude''' (TA) is the altitude above sea level at which aircraft change from the use of local pressure to the use of standard pressure. When operating at or below the TA, aircraft altimeters are usually set to show the altitude above sea level.<ref name="CAP410">{{cite web | title=CAP 410 Manual of Flight Information Services | publisher=UK Civil Aviation Authority | id=CAP410 | url=http://www.caa.co.uk/docs/33/CAP410PtA.pdf | access-date=25 February 2013 }}{{dead link|date=January 2018 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> Above the TA, the aircraft altimeter pressure setting is changed to the standard pressure setting of 1013 [[pascal (unit)|hectopascals]] (equivalent to millibars) or 29.92 [[inches of mercury]], with the aircraft altitude will be stated as a flight level instead of altitude.

In the United States and Canada, the transition altitude is {{cvt|18000|ft|m}}.<ref>{{Cite web|url=https://www.law.cornell.edu/cfr/text/14/91.121|title = 14 CFR § 91.121 - Altimeter settings}}</ref> In Europe, the transition altitude varies and can be as low as {{cvt|3000|ft|-2}}. There are discussions to standardize the transition altitude within the [[Eurocontrol]] area.<ref>{{cite web | title=A Common European Transition Altitude; An ATC perspective | publisher=Eurocontrol | url=https://www.eurocontrol.int/sites/default/files/content/documents/nm/airspace/airspace-atmprocedures-cta-atc-perspective.pdf | access-date=3 April 2014 | url-status=dead | archive-url=https://web.archive.org/web/20130926112255/http://www.eurocontrol.int/sites/default/files/content/documents/nm/airspace/airspace-atmprocedures-cta-atc-perspective.pdf | archive-date=26 September 2013 | df=dmy-all }}</ref> In the United Kingdom, different airports have different transition altitudes, between 3000 and 6000 feet.<ref>{{cite web | url=https://flyinginireland.com/2016/01/iaa-transition-altitude-consultation/ | title=IAA Transition Altitude Consultation | date=17 January 2016 }}</ref>

On 25 November 2004 the [[Civil Aviation Authority of New Zealand]] raised New Zealand's transition altitude from {{convert|11000 to 13,000|ft|m}} and changed the transition level from FL130 to FL150.<ref>{{cite web | title=Part 91, Amendment 12 | publisher=[[Civil Aviation Authority of New Zealand]] | url=http://www.caa.govt.nz/rules/Amendments/Part_091_040705_Amendment_11.pdf | access-date=4 February 2009 | archive-url=https://web.archive.org/web/20160306222005/https://www.caa.govt.nz/rules/Amendments/Part_091_040705_Amendment_11.pdf | archive-date=6 March 2016 | url-status=dead }}</ref>

The '''transition level''' (TL) is the lowest flight level above the transition altitude. The table below shows the transition level according to transition altitude and QNH. When descending below the transition level, the pilot starts to refer to altitude of the aircraft by setting the altimeter to the [[QNH]] for the region or airfield.
{| class="wikitable" align="right"
|+ Table for determining transition level{{Citation needed|date=December 2016}}
|-
!rowspan=2| [[QNH]]<br>(in hectopascals) !! colspan=5 | Transition altitude (in feet)
|-
! 3,000 ft<br>(900 m) !! 4,000 ft<br>(1200 m) !! 5,000 ft<br>(1500 m) !! 6,000 ft<br>(1850 m) !! 18,000 ft<br>(5500 m)
|-
| align="center" | 1032–1050 || FL025 || FL035 || FL045 || FL055 || FL175
|-
| align="center" | 1014–1031 || FL030 || FL040 || FL050 || FL060 || FL180
|-
| align="center" | 996–1013 || FL035 || FL045 || FL055 || FL065 || FL185
|-
| align="center" | 978–995 || FL040 || FL050 || FL060 || FL070 || FL190
|-
| align="center" | 960–977 || FL045 || FL055 || FL065 || FL075 || FL195
|-
| align="center" | 943–959 || FL050 || FL060 || FL070 || FL080 || FL200
|-
|}

The '''transition layer''' is the airspace between the [[transition altitude]] and the [[transition level]].

According to these definitions the transition layer is {{convert|0–500|ft|-1}} thick. Aircraft are not normally assigned to fly at the "'transition level'" as this would provide inadequate separation from traffic flying on QNH at the transition altitude. Instead, the lowest usable "'flight level'" is the transition level plus 500&nbsp;ft.

However, in some countries, such as [[Norway]] for example,<ref>{{cite web |title=Eurocontrol specifications for harmonized Rules for Operational Air Traffic (OAT) under Instrument Flight Rules (IFR) inside controlled Airspace of the ECAC Area (EUROAT) |url=https://www.eurocontrol.int/sites/default/files/2020-01/change-6-eurocontrol-specificatitions-oat-ifr-rules-version-3-0.pdf |website=Eurocontrol |page=63 |language=en }}</ref> the transition level is determined by adding a buffer of minimum {{cvt|1000|ft|m}} (depending on QNH) to the transition altitude. Therefore, aircraft may be flying at both transition level and transition altitude, and still be vertically separated by at least {{cvt|1000|ft|m}}. In those areas the transition layer will be {{cvt|1000|-|1500|ft|m}} thick, depending on QNH.

In summary, the connection between "transition altitude" (TA), "transition layer" (TLYR), and "transition level" (TL) is

TL = TA + TLYR

==Semicircular/hemispheric rule==
The ''semicircular rule'' (also known as the ''hemispheric rule'') applies, in slightly different version, to IFR flights in the UK inside controlled airspace and generally in the rest of the world.
The standard rule defines an East/West track split:

* Eastbound – Magnetic track 000 to 179° – odd thousands (FL 250, 270, etc.)
* Westbound – Magnetic track 180 to 359° – even thousands (FL 260, 280, etc.)

At FL 290 and above, if [[Reduced Vertical Separation Minima]] (RVSM) are not in use, 4,000&nbsp;ft intervals are used to separate same-direction aircraft (instead of 2,000&nbsp;ft intervals below FL 290), and only odd flight levels are assigned, independent of the direction of flight:
* Eastbound – Magnetic track 000 to 179° – odd flight levels (FL 290, 330, 370, etc.)
* Westbound – Magnetic track 180 to 359° – even flight levels (FL 310, 350, 390, etc.)
Conversely, RVSM equipped aircraft are able to continue separation in 2,000&nbsp;ft intervals as outlined in the semicircular rules. Both non-RVSM and RVSM equipped aircraft use a separation of 4,000&nbsp;ft above FL 410. 

Countries where the major airways are oriented north/south (e.g., New Zealand; Italy; Portugal) have semicircular rules that define a North/South rather than an East/West track split.

In Italy, France, Portugal and recently also in Spain (AIP ENR 1.7-3), for example, southbound traffic uses odd flight levels; in New Zealand, southbound traffic uses even flight levels.
In Europe commonly used [[International Civil Aviation Organization]] (ICAO) separation levels are as per the following table:

{| class="wikitable" border="1"
|+ Vertical separation of [[visual flight rules|VFR]] and [[instrument flight rules|IFR]] flights<ref>{{Cite web|date=November 2020|title=Application of Separation Minima|url=https://www.icao.int/EURNAT/EUR%20and%20NAT%20Documents/NAT%20Documents/NAT%20Documents/NAT%20Doc%20008%20-%20NAT%20ASM/NAT%20Doc%20008%20%20(EN)%20-%20Edition%2001,%20Amd%2010.pdf|url-status=dead|access-date=10 October 2021|website=International Civil Aviation Organization|archive-date=2 January 2022|archive-url=https://web.archive.org/web/20220102215351/https://www.icao.int/EURNAT/EUR%20and%20NAT%20Documents/NAT%20Documents/NAT%20Documents/NAT%20Doc%20008%20-%20NAT%20ASM/NAT%20Doc%20008%20%20(EN)%20-%20Edition%2001,%20Amd%2010.pdf}}</ref>
|-
! colspan="8" | Magnetic route figure of merit (FOM)
|-
! colspan="4" | 0° to 179° !! colspan="4" | 180° to 359°
|-
! colspan="2" | VFR !! colspan="2" | IFR !! colspan="2" | VFR !! colspan="2" | IFR
|-
! FL !! feet !! FL !! feet !! FL !! feet !! FL !! feet
|-
| {{n/a}} || {{n/a}} || 010 || 1,000 || {{n/a}} || {{n/a}} || 020 || 2,000
|-
| {{n/a}} || {{n/a}} || 030 || 3,000 || {{n/a}} || {{n/a}} || 040 || 4,000
|-
| 035 || 3,500 || 050 || 5,000 || 045 || 4,500 || 060 || 6,000
|-
| 055 || 5,500 || 070 || 7,000 || 065 || 6,500 || 080 || 8,000
|-
| 075 || 7,500 || 090 || 9,000 || 085 || 8,500 || 100 || 10,000
|-
| 095 || 9,500 || 110 || 11,000 || 105 || 10,500 || 120 || 12,000
|-
| 115 || 11,500 || 130 || 13,000 || 125 || 12,500 || 140 || 14,000
|-
| 135 || 13,500 || 150 || 15,000 || 145 || 14,500 || 160 || 16,000
|-
| 155 || 15,500 || 170 || 17,000 || 165 || 16,500 || 180 || 18,000
|-
| 175 || 17,500 || 190 || 19,000 || 185 || 18,500 || 200 || 20,000
|-
| 195 || 19,500 || 210 || 21,000 || {{n/a}} || {{n/a}} || 220 || 22,000
|-
| {{n/a}} || {{n/a}} || 230 || 23,000 || {{n/a}} || {{n/a}} || 240 || 24,000
|-
| {{n/a}} || {{n/a}} || 250 || 25,000 || {{n/a}} || {{n/a}} || 260 || 26,000
|-
| {{n/a}} || {{n/a}} || 270 || 27,000 || {{n/a}} || {{n/a}} || 280 || 28,000
|-
| {{n/a}} || {{n/a}} || 290 || 29,000 || {{n/a}} || {{n/a}} || 310 || 31,000
|-
| {{n/a}} || {{n/a}} || 330 || 33,000 || {{n/a}} || {{n/a}} || 350 || 35,000
|-
| {{n/a}} || {{n/a}} || 370 || 37,000 || {{n/a}} || {{n/a}} || 390 || 39,000
|-
| {{n/a}} || {{n/a}} || 410 || 41,000 || {{n/a}} || {{n/a}} || 430 || 43,000
|-
| {{n/a}} || {{n/a}} || 450 || 45,000 || {{n/a}} || {{n/a}} || 470 || 47,000
|-
| {{n/a}} || {{n/a}} || 490 || 49,000 || {{n/a}} || {{n/a}} || 510 || 51,000
|}
<!--does 51,000 ft represent an internationally recognised upper limit? -->

==Quadrantal rule==
The quadrantal rule is defunct.<ref>{{Cite web |url=https://www.caa.co.uk/Commercial-industry/Airspace/Rules-of-the-air/SERA-Implementation/ |title=SERA Implementation &#124; UK Civil Aviation Authority |access-date=19 September 2019 |archive-date=7 August 2019 |archive-url=https://web.archive.org/web/20190807012711/http://www.caa.co.uk/commercial-industry/airspace/rules-of-the-air/sera-implementation/ |url-status=dead }}</ref> It was used in the United Kingdom but was abolished in 2015 to bring the UK in line with the semi-circular rule used around the world.<ref>{{cite web|url=http://www.caa.co.uk/sera|title=Standardised European Rules of the Air – UK Civil Aviation Authority|publisher=Civil Aviation Authority|access-date=20 August 2016}}</ref><ref>{{cite web |url=http://flyontrack.co.uk/wp-content/uploads/2015/02/SERA.pdf |title=SERA – all you need to know |author=Dave Drake, CAA Project Lead for SERA  |publisher=flyontrack.co.uk |access-date=20 August 2016}}</ref>

The quadrantal rule applied to [[Instrument flight rules|IFR]] flights in the UK both in and outside of controlled airspace except that such aircraft may be flown at a level other than required by this rule if flying in conformity with instructions given by an air traffic control unit, or if complying with notified en-route holding patterns or holding procedures notified in relation to an aerodrome. The rule affected only those aircraft operating under IFR when in level flight ''above 3,000&nbsp;ft above mean sea level, or above the appropriate transition altitude, whichever is the higher'', and when ''below FL195'' (19,500&nbsp;ft above the 1013.2&nbsp;hPa datum in the UK, ''or'' with the altimeter set according to the system published by the competent authority in relation to the area over which the aircraft is flying if such aircraft is not flying over the UK.){{citation needed|date=September 2019}}

The rule was non-binding upon flights operating under [[visual flight rules]] (VFR).

Minimum vertical separation between two flights abiding by the UK Quadrantal Rule is 500&nbsp;ft (''note these are in [[Geopotential height|geopotential]] foot units''). The level to be flown is determined by the magnetic track of the aircraft, as follows:<ref>Rules of the Air Regulations 2007 (No. 734), rule 34, table 1. Available from the [http://www.statutelaw.gov.uk UK Statute Law Database.]</ref>

* Magnetic track 000 to, and including, 089° – odd thousands of feet (FL070, 090, 110 etc.)
* Magnetic track 090 to, and including, 179° – odd thousands plus 500&nbsp;ft (FL075, 095, 115 etc.)
* Magnetic track 180 to, and including, 269° – even thousands of feet (FL080, 100, 120 etc.)
* Magnetic track 270 to, and including, 359° – even thousands plus 500&nbsp;ft (FL085, 105, 125 etc.)

==Reduced vertical separation minima (RVSM)==

{{main|Reduced vertical separation minima}}

{{hatnote|In the U.S. and Canada, the information in this section applies to flights under [[Instrument flight rules|instrument flight rules (IFR)]]. Different altitudes will apply for aircraft flying under [[Visual flight rules|visual flight rules (VFR)]] above 3000&nbsp;ft AGL.}}

[[Reduced vertical separation minima]] (RVSM) reduces the vertical separation between FL290 and FL410. This allows aircraft to safely fly more optimum routes, save fuel and increase airspace capacity by adding new flight levels. Only aircraft that have been certified to meet RVSM standards, with several exclusions, are allowed to fly in RVSM airspace. It was introduced into the UK in March 2001. On 20 January 2002, it entered European airspace. The United States, Canada and Mexico transitioned to RVSM between FL 290 and FL 410 on 20 January 2005, and Africa on 25 September 2008.

* Track 000 to 179° – odd thousands (FL 290, 310, 330, etc.)
* Track 180 to 359° – even thousands (FL 300, 320, 340, etc.)
At FL 410 and above, 4,000&nbsp;ft intervals are resumed to separate same-direction aircraft and only odd Flight Levels are assigned, depending on the direction of flight:
* Track 000 to 179° – odd flight levels (FL 410, 450, 490, etc.)
* Track 180 to 359° – even flight levels (FL 430, 470, 510, etc.)

==Metre flight levels==
The [[International Civil Aviation Organization]] (ICAO) has recommended a transition to using the [[International System of Units]] since 1979<ref>{{Cite web |url=https://www.icao.int/publications/Documents/9958_en.pdf |title=International Civil Aviation Organization - Assembly Resolutions in Force (as of 8 October 2010) - Doc 9958 - Published by authority of the Secretary General |access-date=26 October 2019 |archive-date=3 May 2022 |archive-url=https://web.archive.org/web/20220503070042/https://www.icao.int/publications/Documents/9958_en.pdf |url-status=dead }}</ref><ref> Council action in pursuance of Assembly Resolution A22-18 adopted 23 March 1979: 
[..]to cover all aspects of air and ground operations; provision of standardized system of units based on the SI; identification of non-SI units permitted for use in international civil aviation; provision for termination of the use of certain non-SI units.</ref> with a recommendation on using metres (m) for reporting flight levels.<ref name="an05_cons">[https://aerosavvy.com/wp-content/uploads/2014/08/an05_cons.pdf International Civil Aviation Organization - International Standards and Recommended Practices - Annex 5 to the Convention on International Civil Aviation - Units of Measurement to be Used in Air and Ground Operations Fifth Edition - July 2010]</ref> China, Mongolia, Russia and many [[Commonwealth of Independent States|CIS]] countries have used flight levels specified in [[metre]]s for years. Aircraft entering these areas normally make a slight climb or descent to adjust for this, although Russia and some CIS countries started using feet above transition altitude and introduced RVSM at the same time on 17 November 2011.

=== Kyrgyzstan, Kazakhstan, Tajikistan, Uzbekistan, and Turkmenistan ===
The flight levels below apply to [[Kyrgyzstan]], [[Kazakhstan]], [[Tajikistan]] and [[Uzbekistan]] and 6,000 m or below in [[Turkmenistan]] (where feet is used for FL210 and above). Flight levels are read as e.g. "flight level 7,500 metres":
{{Col-begin}}
{{Col-break}}
;Track 180 to 359°
*600 m (2,000&nbsp;ft)
*1,200 m (3,900&nbsp;ft)
*1,800 m (5,900&nbsp;ft)
*2,400 m (7,900&nbsp;ft)
*3,000 m (9,800&nbsp;ft)
*3,600 m (11,800&nbsp;ft)
*4,200 m (13,800&nbsp;ft)
*4,800 m (15,700&nbsp;ft)
*5,400 m (17,700&nbsp;ft)
*6,000 m (19,700&nbsp;ft)
*6,600 m (21,700&nbsp;ft)
*7,200 m (23,600&nbsp;ft)
*7,800 m (25,600&nbsp;ft)
*8,600 m (28,200&nbsp;ft)
*9,600 m (31,500&nbsp;ft)
*10,600 m (34,800&nbsp;ft)
*11,600 m (38,100&nbsp;ft)
*13,100 m (43,000&nbsp;ft)
*15,100 m (49,500&nbsp;ft)
and every 2,000 metres thereafter.
{{Col-break}}
;Track 000 to 179°
*900 m (3,000&nbsp;ft)
*1,500 m (4,900&nbsp;ft)
*2,100 m (6,900&nbsp;ft)
*2,700 m (8,900&nbsp;ft)
*3,300 m (10,800&nbsp;ft)
*3,900 m (12,800&nbsp;ft)
*4,500 m (14,800&nbsp;ft)
*5,100 m (16,700&nbsp;ft)
*5,700 m (18,700&nbsp;ft)
*6,300 m (20,700&nbsp;ft)
*6,900 m (22,600&nbsp;ft)
*7,500 m (24,600&nbsp;ft)
*8,100 m (26,600&nbsp;ft)
*9,100 m (29,900&nbsp;ft)
*10,100 m (33,100&nbsp;ft)
*11,100 m (36,400&nbsp;ft)
*12,100 m (39,700&nbsp;ft)
*14,100 m (46,300&nbsp;ft)
and every 2,000 metres thereafter.
{{col-end}}
<!--what is the recognised upper limit? -->

=== People's Republic of China and Mongolia===
The flight levels below apply to [[Mongolia]] and [[People's Republic of China]], not including Hong Kong. To distinguish flight levels in feet, flight levels are read without "flight level", e.g. "one two thousand six hundred metres" or for 12,600 m (Chinese only available in Chinese airspace). To distinguish altitude from flight level, "on standard" or "on QNH" would be added during initial clearance, such as "climb 4,800 metres on standard" or "descent 2,400 metres on QNH 1020".

RVSM was implemented in China at 16:00 UTC on 21 November 2007, and in Mongolia at 00:01 UTC on 17 November 2011. Aircraft flying in feet according to the table below will have differences between the metric readout of the onboard avionics and ATC cleared flight level; however, the differences will never be more than thirty metres.
{{Col-begin}}
{{Col-break}}
;Track 180 to 359°
*600 m (2,000&nbsp;ft)
*1,200 m (3,900&nbsp;ft)
*1,800 m (5,900&nbsp;ft)
*2,400 m (7,900&nbsp;ft)
*3,000 m (9,800&nbsp;ft)
*3,600 m (11,800&nbsp;ft)
*4,200 m (13,800&nbsp;ft)
*4,800 m (15,700&nbsp;ft)
*5,400 m (17,700&nbsp;ft)
*6,000 m (19,700&nbsp;ft)
*6,600 m (21,700&nbsp;ft)
*7,200 m (23,600&nbsp;ft)
*7,800 m (25,600&nbsp;ft)
*8,400 m (27,600&nbsp;ft)
*9,200 m (30,100&nbsp;ft)
*9,800 m (32,100&nbsp;ft)
*10,400 m (34,100&nbsp;ft)
*11,000 m (36,100&nbsp;ft)
*11,600 m (38,100&nbsp;ft)
*12,200 m (40,100&nbsp;ft)
*13,100 m (43,000&nbsp;ft)
*14,300 m (46,900&nbsp;ft)
and every 1,200 metres thereafter.
{{Col-break}}
;Track 000 to 179°
*900 m (3,000&nbsp;ft)
*1,500 m (4,900&nbsp;ft)
*2,100 m (6,900&nbsp;ft)
*2,700 m (8,900&nbsp;ft)
*3,300 m (10,800&nbsp;ft)
*3,900 m (12,800&nbsp;ft)
*4,500 m (14,800&nbsp;ft)
*5,100 m (16,700&nbsp;ft)
*5,700 m (18,700&nbsp;ft)
*6,300 m (20,700&nbsp;ft)
*6,900 m (22,600&nbsp;ft)
*7,500 m (24,600&nbsp;ft)
*8,100 m (26,600&nbsp;ft)
*8,900 m (29,100&nbsp;ft)
*9,500 m (31,100&nbsp;ft)
*10,100 m (33,100&nbsp;ft)
*10,700 m (35,100&nbsp;ft)
*11,300 m (37,100&nbsp;ft)
*11,900 m (39,100&nbsp;ft)
*12,500 m (41,100&nbsp;ft)
*13,700 m (44,900&nbsp;ft)
*14,900 m (48,900&nbsp;ft)
and every 1,200 metres thereafter.
{{col-end}}
<!--what is the recognised upper limit? -->

==Flight levels in Russian Federation and North Korea==
On 5 September 2011 the government of the [[Russian Federation]] issued decree No.743,<ref>{{cite web|title=Постановление Правительства РФ от 05.09.2011 N 743|url=http://base.consultant.ru/cons/cgi/online.cgi?req=doc;base=LAW;n=119021#|publisher=Консультант Плюс|language=ru|trans-title=Checked on September 5, 2011: N 743, AMENDING In the federal regulations of air space use RUSSIAN FEDERATION|access-date=29 September 2011|url-status=dead|archive-url=https://web.archive.org/web/20160203091332/http://base.consultant.ru/cons/cgi/online.cgi?req=doc%3Bbase%3DLAW%3Bn%3D119021|archive-date=3 February 2016}}</ref> pertaining to the changes in the rules of use of the country's airspace. The new rules came into force on 17 November 2011, introducing a flight level system similar to the one used in the West. RVSM has also been in force since this date.

The following table is true for IFR flights:

{{Col-begin}}
{{Col-break}}
;Track 180 to 359°
{| class="wikitable" border="1"
!       FL	!!     (metres)	!!	(feet)
|-
||	20	||	600	||	2000
|-					
||	40	||	1200	||	4000
|-					
||	60	||	1850	||	6000
|-					
||	80	||	2450	||	8000
|-					
||	100	||	3050	||	10000
|-					
||	120	||	3650	||	12000
|-					
||	140	||	4250	||	14000
|-					
||	160	||	4900	||	16000
|-					
||	180	||	5500	||	18000
|-					
||	200	||	6100	||	20000
|-					
||	220	||	6700	||	22000
|-					
||	240	||	7300	||	24000
|-					
||	260	||	7900	||	26000
|-					
||	280	||	8550	||	28000
|-					
||	300	||	9150	||	30000
|-					
||	320	||	9750	||	32000
|-					
||	340	||	10350	||	34000
|-					
||	360	||	10950	||	36000
|-					
||	380	||	11600	||	38000
|-					
||	400	||	12200	||	40000
|-					
||	430	||	13100	||	43000
|-					
||	470	||	14350	||	47000
|-					
||	510	||	15550	||	51000
|}
{{Col-break}}
;Track 000 to 179°
{| class="wikitable" border="1"
!       FL	!!     (metres)	!!	(feet)
|-
|	10 	||	300	||	1000
|-					
|	30	||	900	||	3000
|-					
|	50	||	1500	||	5000
|-					
|	70	||	2150	||	7000
|-					
|	90	||	2750	||	9000
|-					
|	110	||	3350	||	11000
|-					
|	130	||	3950	||	13000
|-					
|	150	||	4550	||	15000
|-					
|	170	||	5200	||	17000
|-					
|	190	||	5800	||	19000
|-					
|	210	||	6400	||	21000
|-					
|	230	||	7000	||	23000
|-					
|	250	||	7600	||	25000
|-					
|	270	||	8250	||	27000
|-					
|	290	||	8850	||	29000
|-					
|	310	||	9450	||	31000
|-					
|	330	||	10050	||	33000
|-					
|	350	||	10650	||	35000
|-					
|	370	||	11300	||	37000
|-					
|	390	||	11900	||	39000
|-					
|	410	||	12500	||	41000
|-					
|	450	||	13700	||	45000
|-					
|	490	||	14950	||	49000
|}
{{col-end}}

The new system would eliminate the need to perform climbs and descents in order to enter or leave Russian airspace from or to jurisdictions following the Western standard.<ref>{{cite web |url=http://www.rusaero.aero/files/679/aic-2011-11ang.pdf |title=About the Transition to the ICAO Vertical Separation System and Reduced Vertical Separation Minimum (RVSM) From FL 290 TO FL 410 Inclusive in the Airspace of the Russian Federation Effective From 17 November 2011 |publisher=rusaero.aero |date=20 November 2011 |access-date=20 August 2016 |archive-date=15 April 2016 |archive-url=https://web.archive.org/web/20160415045050/http://www.rusaero.aero/files/679/aic-2011-11ang.pdf |url-status=dead }}</ref>

From February 2017, Russia is changing to use QNH and Feet below the Transition Level. The first airport to use this is ULLI/St. Petersburg.<ref>{{Cite web|first1=Declan |last1=Selleck |date=2017-02-22|title=Big change: Russia finally moving to QNH|url=https://ops.group/blog/big-change-russia-finally-moving-to-qnh/|access-date=2021-07-18|website=International Ops 2021|language=en-US}}</ref> Most other airports still{{As of?|date=April 2023}} use QFE.

Unlike Russia, North Korea uses metres below the TL based on QNH.

==See also==
* [[International Civil Aviation Organization#International System of Units|ICAO recommendations on use of the International System of Units]]
*[[Flight planning]]
*[[Gillham code]]

==References==
{{reflist|colwidth=30em}}<!--added above categories/infobox footers by script-assisted edit-->

{{DEFAULTSORT:Flight Level}}
[[Category:Altitudes in aviation]]
[[Category:Air traffic control]]