example: an airplane crossing the Atlantic passes the point (somewhere beyond the center point of the flight, hopefully) after which it would be impossible to successfully return to the point of origin; there is not enough fuel to make it so turning around would result in the plane running out of fuel and plunging into the ocean.

Having passed "the point of no return" does not neccessarily involve planes or crashes; the term can be used to express determination toward the completion or realization of some goal, project or end.