Definition
A point along an over-water or remote route, calculated before flight, from which it would take the same time to continue to the destination as to return to the departure airport (or to divert to a suitable alternate), taking into account forecast winds and aircraft performance. Also called the equal-time point (ETP) or point of equal time (PET).
Plain English
The spot on a long flight where going forward and turning back would take exactly the same amount of time. Past this point, it's quicker to keep going than to turn around.
Context Anchor
Seen in navigation and flight planning, especially on long flights over water, mountains, or remote areas where the best direction to go after a problem may not be obvious.
Derivation
Critical' comes from the Greek 'krisis,' meaning a turning point or decisive moment. The term fits because this is the decision point on the flight where 'forward' and 'back' become equal — the moment where a diversion choice tips one way or the other.
Why Pilots Care
It tells the pilot the last safe moment to turn back before fuel reserves become insufficient for either option.
Analogy
It is like driving between two towns and reaching the place where it would take the same time to go back home as to keep going to the next town.
Intuition Check
Critical does not mean the airplane is in immediate danger here. It means this is the decision point where the time to go forward and the time to go back are equal.
Example Sentence 1
Before the transatlantic crossing, the crew calculated the critical point at 32°W, accounting for the forecast 40-knot headwind component.
Example Sentence 2
After passing the critical point the crew continued to the destination instead of turning back.