Composition of flight crew

This regulation establishes minimum flight crew requirements for Part 121 air carrier operations.

Airlines must provide at least the minimum crew specified in the aircraft's airworthiness certificate or flight manual, whichever this regulation requires for the operation. You cannot have one pilot performing multiple required crew functions simultaneously—if two certificated positions are required, two separate people must fill them.

The minimum crew is always two pilots: one designated as pilot in command and one as second in command, regardless of what the aircraft certification might otherwise allow.

If the flight requires a flight engineer, at least one other crew member (typically a pilot) must be qualified to perform the flight engineer's emergency duties if the engineer becomes incapacitated. This backup crew member doesn't need a flight engineer certificate—just the ability to handle those functions in an emergency to complete the flight safely.

*This is a plain-English summary for study only. The official 14 CFR text on this page is controlling — always read the current regulation and consult a CFI.*