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Flight Level (FL) A surface of constant atmosphere pressure which is related to a specific pressure datum, 1013.2hPa, and is separated from other such surfaces by specific pressure intervals. Altitude above sea-level in 100 feet units measured according to a standard atmosphere.
25 sty 2024 · A flight level (FL) is a standard pressure altitude, expressed as three numbers. Aircraft flying on flight levels all measure their altitude from the same pressure setting, 1013.2 Hpa (or 29.92 InHg).
The air pressure is computed assuming an International Standard Atmosphere pressure of 1013.25 hPa (29.92 inHg) at sea level, and therefore is not necessarily the same as the aircraft's actual altitude, either above sea level or above ground level.
As for the air pressure on the International Space Station being one bar, technically the atmospheric pressure could be lower, but it couldn't be as low as it is near Mount Everest's summit because humans could only survive those pressures a few minutes at most.
Cabin pressure (psi) – ambient pressure (psi) = cabin differential pressure (psid or Δ psi). Cabin rate of climb—the rate of change of air pressure inside the cabin, expressed in feet per minute (fpm) of cabin altitude change.
The correct transmission of FL 100 (i.e. "FLIGHT LEVEL ONE ZERO ZERO" or "FLIGHT LEVEL ONE ONE ZERO") differs by country and has also changed over time. Currently, ICAO standard phraseology (as specified in Annex 10, Volume II, Chapter 5, 2018) prescribes the use of whole hundreds for flight levels.
Flight Level specifically refers to Pressure Altitude in 100 foot increments within the Standard Pressure Region, which in North America starts at 18000 ft and above, and at various lower altitudes elsewhere.
