Definition
The minimum amount of usable fuel a pilot must have on board before beginning a flight, as set by the Federal Aviation Regulations. Under 14 CFR 91.151, a VFR flight must carry enough fuel to fly to the first point of intended landing and then continue at normal cruising speed for at least 30 minutes during the day or 45 minutes at night. IFR flights have stricter requirements, including fuel to reach the destination, fly to an alternate airport when one is required, and then fly for an additional 45 minutes at normal cruising speed.
Plain English
The legal minimum fuel a pilot must have before takeoff: enough to reach the destination plus a reserve to keep flying for a set time after that.
Context Anchor
You encounter this during preflight planning, especially when deciding whether the fuel on board is enough for the route, conditions, and required reserve.
Why Pilots Care
Fuel exhaustion remains a leading cause of general-aviation incidents; meeting these requirements keeps the flight both legal and safe.
Intuition Check
Do not read fuel requirements as just the fuel needed to reach the destination. In aviation, it includes required extra fuel and planning margin for the whole flight.
Example Sentence 1
Before departing on the cross-country, she calculated the fuel requirements for the flight and added an extra 30 minutes on top of the legal reserve.
Example Sentence 2
The instructor reminded the student to add a 30-minute reserve when calculating fuel requirements for the night cross-country.