Point of no return calculator
The point of no return is the furthest you can go and still turn round and make it home on the fuel you have. Past it, going back is no longer an option.
Calculator
This is an educational and planning aid. Use current official weather, your aircraft flight manual, and the rules that apply to your flight before you act on any figure here. See the aviation disclaimer.
What the result means
The answer is a distance from departure, together with the time it takes to get there and the time it would take to fly home from there.
Those two times added together equal the endurance you entered, which is what makes this the limit. Every mile beyond it is a mile you cannot undo.
It says nothing about whether you can reach your destination or any other airfield. It is only about getting back to where you started.
When this is useful
- Any flight over water, desert, mountains or anywhere else without a usable airfield along the route.
- Ferry flights and long range legs where fuel, not time, is the binding constraint.
- Understanding the difference between a fuel limit and a time limit, which is what separates this from the equal time point.
How it is calculated
Take the endurance available and split it between an outbound leg and a return leg, so that the distance out equals the distance back. Solving that gives endurance multiplied by both groundspeeds, divided by their sum.
The endurance you enter must already have the reserve taken off. The calculator deliberately does not assume a reserve, because reserve requirements differ by country, by operation, and by aircraft.
PNR distance = endurance x GS out x GS back / (GS out + GS back)
Worked example
- Usable endurance after reserve
- 5 hours
- Groundspeed outbound
- 400 kt
- Groundspeed on the return
- 500 kt
The point of no return is 1,111 NM out, reached after 2 hours 47 minutes. The flight home from there takes 2 hours 13 minutes.
Check: 2 hours 47 minutes out plus 2 hours 13 minutes back is exactly 5 hours, the endurance entered. The outbound distance at 400 kt is 1,111 NM and the return distance at 500 kt is also 1,111 NM, so both legs cover the same ground.
Limitations
- The answer is only as good as the endurance you entered. If you entered total endurance rather than endurance after reserve, the calculation lands you back home with dry tanks.
- Groundspeeds change with the actual wind, and the return wind is a forecast at the time you plan. Recheck in flight.
- It assumes you would return to the departure airfield. If a closer airfield is available the real decision point is different.
Common mistakes
- Forgetting to subtract the reserve before entering endurance. This is the single most serious error on this page.
- Using the same groundspeed in both directions when there is a significant wind.
- Treating the result as a fixed point on the chart. It moves as the actual winds and fuel burn differ from plan.
Sources
- Extended-range flying: point of no return , Aircraft Owners and Pilots Association
- Pilot's Handbook of Aeronautical Knowledge, navigation chapter , US Federal Aviation Administration