Flight Fuel Planning Explained: Trip, Contingency, Alternate and Reserve
Fuel planning answers one question: how much fuel must be on board at engine start so the flight can be completed safely, including a diversion and a reserve? The answer is called block fuel, and it is built from several parts.
The parts of block fuel
- Taxi fuel: burned from engine start to takeoff.
- Trip fuel: from takeoff to landing at the destination, including climb, cruise and descent.
- Contingency fuel: covers unexpected extra burn. A common figure under ICAO standards is 5 percent of the trip fuel, though other methods are allowed.
- Alternate fuel: to fly from the destination to the alternate airport, if one is required.
- Final reserve: ICAO standards set 30 minutes for turbine-engine aircraft and 45 minutes for piston-engine aircraft, at holding speed 1,500 ft above the aerodrome.
- Additional fuel: extra fuel the operator or commander adds for weather, delays or other risks.
Worked example
A 300 NM trip at 120 knots ground speed takes 2 hours 30 minutes. At a burn of 40 per hour, trip fuel is 100. Contingency at 5 percent is 5. Final reserve of 30 minutes is 20. Alternate fuel is 25 and taxi fuel is 3. Block fuel = 3 + 100 + 5 + 25 + 20 = 153. Use the same unit throughout, such as kilograms, pounds or litres.
Why the rules differ
Regulators set their own minimums. The United States, Europe and other States each have their own reserve and alternate rules for different types of operation. Always follow your own regulator and your operator's fuel policy. The calculator on this site uses a simple version, with the reserve flown at cruise burn, so treat it as a teaching tool.
Open the fuel planning calculator
FAQ
What is final reserve fuel?
The fuel that must still be on board at landing so the aircraft can hold for a set time, normally 30 or 45 minutes. It is not for planning use and is only touched in an emergency.
Is contingency fuel the same as extra fuel?
No. Contingency is a planned allowance for unexpected burn. Extra, or additional, fuel is added on top for specific risks.
More guides
- How to Calculate Crosswind and Headwind Components
- How to Read a METAR: A Plain-English Guide
- How to Read a TAF: Airport Forecasts Explained
- What Is in an ICAO Flight Plan? Every Item Explained
- The Wind Triangle Explained: Heading, Ground Speed and Drift
- FAA Part 117 Explained: Flight Time, Duty Period and Rest
- Density Altitude Explained: How Heat and Height Cut Performance
- How to File a Flight Plan: Steps for Pilots and Dispatchers
- How to Read a NOTAM: ICAO Format Explained
For training and reference only. Check official sources before any real flight.