point of no return

Meanings

1. The point in an aircraft's flight when there is insufficient fuel to reverse direction and return to the place of origin.
2. The point in any process or sequence of events where some development becomes inevitable.

Etymology

The expression originated in air navigation planning. The point along the planned flight path beyond which an aircraft will no longer be capable of returning to the takeoff airfield or an alternate airfield due to insufficient fuel is calculated before takeoff. This is mandatory for overwater flights or flights without alternates on route.