Definition
The altitude listed by the pilot in the flight plan filed with ATC for the en route portion of an IFR or VFR flight.
Plain English
The cruising altitude you wrote down on your flight plan when you submitted it before the flight.
Context Anchor
You will see this in instrument departure clearances, especially in phrases such as “expect filed altitude ten minutes after departure.”
Derivation
‘Filed’ comes from the practice of submitting (filing) a flight plan with ATC before departure. The altitude entered on that form becomes the ‘filed altitude.’
Why Pilots Care
ATC may clear you to climb to the filed altitude after departure, sometimes via the phrase ‘climb to and maintain filed altitude.’ Knowing exactly what you filed prevents confusion when that clearance is issued.
Intuition Check
Do not read “filed altitude” as “the altitude I am cleared to fly now.” It means the altitude written in the flight plan; clearance to climb to it may come later.
Example Sentence 1
After takeoff, the controller said, ‘Climb and maintain filed altitude,’ so the pilot continued up to 8,000 feet as listed on the flight plan.
Example Sentence 2
ATC cleared the aircraft to its filed altitude shortly after takeoff.