Point of No Return

The Point of No Return (PNR) — also called the Point of Safe Return (PSR) — is the last geographic point along a route from which an aircraft can return to the departure airport (or another suitable airport behind it) with the required fuel reserves still intact. Beyond the PNR, the aircraft is committed to continuing to the destination or an alternate ahead.

PNR calculation is a standard element of oceanic and long-distance flight planning. The formula accounts for:

• Total usable fuel at the PNR
• Fuel required for the return leg (including headwind component)
• Required reserve fuel at the return airport
• Any fuel needed for holding or diversion

A related concept is the Equal Time Point (ETP) or Critical Point (CP), which is the point along the route where the time to continue to the destination equals the time to return. The ETP and PNR are different points — the ETP is about time, the PNR is about fuel.