When should a pilot declare minimum or emergency fuel?

A pilot should declare minimum or emergency fuel based on the condition where it becomes apparent that the fuel remaining will be less than the required minimum for a safe landing. This declaration is important because it alerts air traffic control and other relevant parties that the aircraft may require priority handling to land safely due to fuel constraints.

Declaring when the fuel is lower than normal recovery levels does not necessarily indicate that a critical situation is at hand, as some safety margins are typically maintained. Similarly, stating a threshold based on half-fuel capacity might not accurately represent the urgency of the situation since the actual fuel required can vary depending on flight conditions, payload, and destination requirements. Lastly, experiencing fuel system anomalies may warrant attention, but it doesn’t directly correlate with fuel remaining being below necessary levels for safe landing.

Therefore, the most appropriate condition to declare minimum or emergency fuel involves being actively aware that the remaining fuel will not meet the requirements for a safe landing.