Running out of fuel is one of the most avoidable ways to lose an aircraft, which is why the rules never let you carry only what the trip itself needs.
This is general educational information, not operational, legal, or regulatory advice. Rules differ by authority and change over time. Always verify against current official sources and follow your operator's approved procedures.
The principle, and the ICAO baseline
Fuel planning answers a simple question with a margin built in: enough fuel to fly the planned route, reach an alternate if you cannot land at the destination, and still have a reserve untouched on arrival. The international baseline is ICAO Annex 6, which requires that a flight not begin unless it carries enough fuel to complete it safely, taking account of the conditions and of alternates, and which frames the modern fuel-planning schemes. The detailed figures, though, are written by each authority, and they differ, so attribute every reserve time or percentage to its source.
The FAA rules
In the United States the reserves are stated as flat times, in 14 CFR Part 91 for general operations and Part 121 for airlines:
- VFR, aeroplanes (14 CFR 91.151): enough fuel to fly to the first point of intended landing and then, at normal cruising speed, for at least 30 minutes by day or 45 minutes by night.
- IFR (14 CFR 91.167): enough to fly to the destination, then to the most distant required alternate, then for 45 minutes at normal cruising speed (with a different figure for helicopters).
- Domestic airline operations (14 CFR 121.639): enough to fly to the destination, then to the most distant required alternate, then for 45 minutes at normal cruising fuel consumption.
These are the FAA's figures; they are not EASA's and they are not universal.
The EASA fuel scheme
EASA does not use a single reserve time. Its Air Operations rules, restructured by Regulation (EU) 2021/1296 and now in CAT.OP.MPA.180 and CAT.OP.MPA.181, require the usable fuel (or energy) to be built from named components:
- Taxi fuel for ground movement before take-off;
- Trip fuel to fly from take-off to landing at the destination;
- Contingency fuel to cover unforeseen deviations from the plan;
- Destination-alternate fuel to reach the alternate if one is required;
- Final reserve fuel, a protected minimum based on a holding time at the alternate (or destination) that you should not plan to use;
- Additional fuel and discretionary (extra) fuel as the situation or the commander requires.
The exact percentages and times attach to these components in the regulation, and they are revised over time, so read the current EASA Air Operations rules for the figures rather than memorising a number. The structure, not a single reserve time, is what makes the EASA scheme different from the FAA's.
Conceptually the components stack up into the fuel you load: taxi fuel for the ground movement, then trip fuel for the planned flight, then contingency fuel for the unexpected, then destination-alternate fuel to divert, then the final reserve that should still be there on arrival, with any additional and discretionary fuel on top. Seen that way, the value of the scheme is plain: it forces every part of the journey, including the parts you hope not to fly, to be accounted for in its own right rather than buried inside a single round figure.
Why the margin is never optional
Reserves are minimums, not targets. The real fuel figure has to absorb headwinds stronger than forecast, a runway change that lengthens the taxi, holding for traffic or weather, a missed approach and diversion, and the simple fact that the unusable fuel in the tanks cannot be burned. A tank that is physically full is not the same as a flight that is legally and sensibly fuelled, because what matters is fuel against the planned route and its contingencies, not litres in the wings. When the plan is tight, the answer is more fuel or a shorter leg, not optimism.
Common pitfalls
- Treating the reserve as usable. Final reserve fuel exists to still be there on arrival, not to extend the flight.
- Assuming one number fits. The FAA's 30 and 45 minutes are FAA Part 91 figures; EASA uses a component scheme; airline rules differ again.
- Ignoring the conditions. Wind, weather, holding, and a possible diversion all push the required figure above the bare minimum.
- Forgetting unusable fuel and the figures change. Some fuel cannot be used, and the regulations are amended, so check the current rule for your operation.
In Pilot EFB
Pilot EFB does not calculate fuel or reserves, and it is not a certified Electronic Flight Bag. It is a study and planning aid that keeps your weather, NOTAMs, flight time, and logbook in one offline-first place, which helps you judge the conditions a fuel plan has to survive. Work the fuel itself from the approved aircraft data and your operator's fuel policy, and treat the regulation for your operation as the binding requirement. Saved data stays readable offline; pulling fresh data needs a connection.