What Is a Flight Level?
Why pilots and ATC use "FL350" instead of 35,000 feet. The simple, accurate 2026 explainer.
The 30-second answer
A flight level is altitude expressed in hundreds of feet, with the altimeter set to the standard pressure of 29.92 inHg / 1013.25 hPa instead of local pressure. FL350 = 35,000 ft on the standard altimeter.
Why it exists
Above the transition altitude (typically 18,000 ft in the US, 5,000–6,000 ft in much of Europe), aircraft set the standard pressure. This guarantees that two aircraft at "FL350" are at the same altitude relative to each other regardless of local pressure changes — critical for vertical separation.
What you'll hear
"Climbing to flight level three-five-zero" = climbing to 35,000 ft on the standard altimeter setting.
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