Definition
The minimum quantity of usable fuel an aircraft must carry beyond the amount needed to reach the intended destination, as required by regulation. Under 14 CFR 91.151, day VFR flights require fuel to fly to the first point of intended landing plus 30 minutes at normal cruise; night VFR requires 45 minutes. IFR fuel requirements under 14 CFR 91.167 require fuel to reach the destination, then the alternate (if required), plus 45 minutes at normal cruise.
Plain English
Extra fuel you must have on board, on top of what it takes to fly to where you are going. The rules set a minimum so you still have flying time left if something goes wrong on arrival.
Context Anchor
You will meet this term during preflight planning, fuel checks, and decisions about whether to continue, divert, or land for fuel.
Derivation
Reserve' comes from the Latin 'reservare,' meaning to keep back or hold in store. The fuel reserve is fuel held back — set aside untouched — for the unexpected.
Why Pilots Care
Running out of fuel is a leading cause of general aviation accidents. Carrying required reserves ensures both regulatory compliance and a practical safety margin.
Intuition Check
Do not think of fuel reserves as optional leftover fuel. In aviation, fuel reserves are a planned safety margin that should still be available after the expected flight fuel is accounted for.
Example Sentence 1
After calculating the trip fuel, she added the required 45-minute night VFR fuel reserves before deciding the tanks held enough for the flight.
Example Sentence 2
For the VFR cross-country, regulations required enough fuel to reach the airport plus 30 minutes of reserves.