FAA Aircraft Dispatcher (ADX)Flight Planning and PerformanceEasy
A Part 121 domestic dispatcher is releasing a flight under IFR to a destination that requires an alternate. Under 14 CFR 121.639, the aircraft must carry enough fuel to fly to the destination airport, then to the alternate, and then for how long at normal cruising fuel consumption?
- A45 minutes
- B90 minutes
- C30 minutes
- D60 minutes
Show answer & explanationAnswer & explanation
Correct answer: A. 45 minutes
14 CFR 121.639 requires domestic Part 121 operations to carry sufficient fuel to fly to the destination, then to the alternate, and then to fly for 45 minutes at normal cruising fuel consumption.
Why the other options are wrong
- B. 90 minutes is not a standard reserve fuel figure under Part 121.
- C. 30 minutes is the flag/international reserve under 121.645, not domestic.
- D. 60 minutes exceeds the regulatory minimum for domestic operations.
Domestic Fuel Reserve (121.639)
For domestic Part 121 IFR flights, fuel must cover flight to destination, to the alternate, plus 45 minutes at normal cruise fuel consumption.
- Applies to domestic operations under 121.639
- 45-minute reserve at normal cruising consumption
- Flag operations (121.645) use a 30-minute reserve instead
Memory trick: Domestic = 45, Flag = 30 — 'Home needs more gas.'