Learn how much reserve fuel to carry in a flight simulator, with practical VFR, IFR and airliner baselines and a clear calculation method.
In a flight simulator, plan reserve fuel to match the rules and aircraft you are simulating, not as a flat tank percentage. For an ICAO-style airline plan, final reserve is commonly 30 minutes for a turbine aircraft or 45 minutes for a piston aircraft; contingency and alternate fuel are separate amounts.
For Aviation & Real-World Flying scenarios, there is no universal reserve figure. The applicable flight rules, aircraft type, weather, alternate and operator procedures determine what must remain. If you are reproducing a real operation, its flight plan or operating rules take precedence over these practical baselines.
What counts as reserve fuel?
Final reserve is protected fuel intended to remain when the aircraft lands; it is not the entire margin carried above trip fuel. A complete block-fuel calculation may contain taxi, trip, contingency, alternate, final-reserve and extra fuel.
If an alternate is required, you should reach the destination with enough fuel to fly to that alternate and still land with final reserve. Our breakdown of block, trip, alternate and final-reserve fuel explains how these quantities fit together.
Which reserve rule should I use?
Choose the rule that matches the operation being simulated rather than applying one percentage to every flight.
| Type of simulated flight | Practical planning basis | What remains separate |
|---|---|---|
| Casual general-aviation flight | Plan to land with at least 45 minutes at a realistic cruise or loiter fuel flow | Extra fuel for poor weather, circuits or delays |
| US-style VFR aeroplane flight | Common legal baseline is 30 minutes by day or 45 minutes by night at normal cruising consumption | Any prudent weather or route margin |
| US-style IFR flight | Fuel to the destination, then the alternate when required, followed by 45 minutes at normal cruise | Taxi and any additional delay allowance |
| ICAO-style airline flight | Contingency fuel, alternate fuel and final reserve; final reserve is commonly 30 minutes for turbine aircraft or 45 minutes for piston aircraft | Taxi, discretionary extra fuel and special operational requirements |
Airline contingency is often based on 5% of trip fuel, but approved reduced-contingency and statistical schemes exist. Final reserve for a turbine airliner is normally calculated at holding speed about 1,500 feet above the relevant aerodrome under defined conditions, not at high-altitude cruise burn.
How do I calculate reserve fuel in the simulator?
Convert the required reserve time into fuel using the expected consumption at the specified flight condition.
- Select the rule set. Decide whether the flight is casual VFR, regulatory VFR or IFR, or an airline-style dispatch.
- Estimate trip fuel. Include climb, cruise, descent and approach, using the aircraft's performance data or a reliable planning tool.
- Add contingency and alternate fuel. Do not hide these inside final reserve. Alternate fuel must cover the missed approach, diversion, approach and landing assumptions used by your plan.
- Convert reserve time to quantity. Use
final reserve = reserve time in hours × applicable fuel flow. At 9 US gallons per hour, a 45-minute reserve is 6.75 usable US gallons. - Add operational extra fuel. Allow for forecast weather, extended taxi, expected holding, repeated approaches or uncertain simulator fuel modelling.
- Check aircraft limits. Confirm usable tank capacity, take-off mass and predicted landing mass before loading the result.
For a light piston aircraft, our guide to Cessna 172 burn rates and usable-fuel planning shows how mixture, power and flight time affect the calculation. For more complex flights, use a complete simulator dispatch workflow with realistic fuel planning rather than guessing from the fuel-slider percentage.
What should I enter as reserves in the FMC?
The FMC reserve entry is usually a prediction or warning threshold; it does not load that fuel into the aircraft. Depending on the aircraft and operator convention, the value may represent final reserve alone or a minimum landing figure that includes alternate fuel.
Follow the add-on documentation or operational flight plan, and compare predicted destination fuel with the required landing fuel. The fuel itself must still be loaded through the simulator or aircraft fuel manager. Our explanation of reserve entries and fuel predictions in a Boeing 737 FMC covers the airliner workflow.
When should I carry extra fuel?
Carry extra fuel when a foreseeable risk is not adequately covered by the basic calculation. Typical reasons include strong or uncertain winds, thunderstorms near the destination, de-icing, long taxi queues, a distant alternate, limited diversion airports or planned approach practice.
Extra fuel is not permission to reduce final reserve. In a realistic flight, if updated predictions show that landing fuel will fall below the protected minimum, the correct response is normally to divert, land earlier or revise the plan—not continue until the tanks reach the reserve figure.
Which reserve-fuel mistakes cause problems?
- Loading an arbitrary tank percentage: 20% may be excessive for one flight and unsafe for another because it ignores fuel flow and diversion distance.
- Counting alternate fuel as final reserve: the alternate leg consumes its own fuel; final reserve should remain after that diversion.
- Using total rather than usable capacity: trapped or unusable fuel cannot be included in endurance calculations.
- Mixing units: check kilograms, pounds, litres and US gallons carefully, including the density conversion used by the simulator.
- Using cruise burn for every phase: taxi, climb, holding and low-altitude operation can differ substantially from cruise consumption.
- Entering block fuel in the FMC reserve field: this produces misleading warnings and predictions even when the tanks contain the correct amount.