Editing Flight level (section)

{{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{{Outdated as of | topic = usage of metric flight levels in Kyrgyzstan, Kazakhstan, Tajikistan, Uzbekistan, and Turkmenistan | last updated = | year = 2024 | month = 12 |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]]