Definition
The airspeed at which an aircraft burns the least amount of fuel per unit of time, allowing it to remain airborne for the longest possible duration on a given quantity of fuel. It corresponds to the speed where total drag is at its lowest, requiring the least power to maintain level flight.
Plain English
The speed that lets the aircraft stay in the air the longest on the fuel it has, by burning fuel as slowly as possible. It is about time aloft, not distance covered.
Context Anchor
Seen in performance charts and in discussions of the region of reversed command, especially when comparing speeds for maximum time aloft versus maximum distance.
Derivation
‘Endurance’ comes from Old French endurer, meaning ‘to last’ or ‘to hold out.’ In aviation it carries that same sense: how long the aircraft can last in the air before running out of fuel.
Why Pilots Care
Maximizes time aloft during holds, searches, or fuel-critical situations without changing altitude.
Intuition Check
Best does not mean best for every purpose. Here, best means longest time in the air; it does not mean fastest speed or greatest distance covered.
Example Sentence 1
While waiting for the runway to reopen, the pilot slowed to best endurance airspeed to stay airborne as long as possible.
Example Sentence 2
Selecting best endurance airspeed allowed the aircraft to remain on station for an additional twenty minutes on the remaining fuel.