Point of no return

The point of no return (PNR or PONR) is the point beyond which one must continue on one's current course of action because turning back is physically impossible, prohibitively expensive, or dangerous. A particular irreversible action (e.g., setting off an explosion or signing a contract) can be a point of no return, but the point of no return can also be a calculated point during a continuous action (such as in aviation).

The term "point of no return" originated as a technical term in air navigation to refer to the point on a flight at which a plane is no longer capable of returning to the airfield from which it took off.

The first major metaphorical use of the term in popular culture was in the 1947 novel Point of No Return by John P. Marquand. It inspired a 1951 Broadway play of the same name by Paul Osborn. The novel and play concern a pivotal period in the life of a New York City banker. In the course of the story, the character faces two "point of no return" realities: First, that his quest for a big promotion will mean either triumph or a dead end to his career, and second, that he can never go back to the small-town life he abandoned as a young man.

There are a number of phrases with similar or related meaning:

The Point of Safe Return (PSR) is the last point on a route at which it is possible to return to the departure airfield with the required fuel reserves still available in the tanks. Continuing past the PSR, one is now committed to landing at your destination.

The following expressions also express the idea of a point of no return.

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