ETP and PNR Calculator
The equal time point (ETP) is where going on and going back take the same time; the point of no return (PNR) is the furthest you can fly and still return with your reserve. Enter distance, groundspeeds and safe endurance.
Planning aid only. Use your operator’s flight plan, forecast winds for each segment and the speeds for the scenario you are planning (all engines, engine out or depressurised).
How the ETP and PNR are calculated
- Distance to ETP = D × H ÷ (O + H). Time to ETP = that distance ÷ O.
- Time to PNR = E × H ÷ (O + H). Distance to PNR = that time × O.
- With a headwind outbound (O < H), both points move beyond halfway.
Worked example
1,200 NM leg, 400 kt groundspeed on, 500 kt home, 5 h safe endurance. ETP = 1,200 × 500 ÷ 900 = 666.7 NM, reached after 1 h 40 min. From there, going on or going back both take 80 minutes. PNR = 5 × 500 ÷ 900 = 2.78 h (2 h 47 min), at 1,111 NM.
Tip: work out one ETP per scenario. An engine-out ETP uses a lower TAS and level than a medical-diversion ETP, so it falls in a different place.
Read the guide: Equal Time Point and Point of No Return Explained
Method from standard flight-planning theory (FAA Aircraft Dispatcher and EASA ATPL syllabi).
Last reviewed: November 2026
Frequently asked questions
Does fuel change the ETP?
No. The ETP depends only on distance and the two groundspeeds. Fuel limits the PNR.
What endurance should I enter?
Usable fuel minus the reserve you must keep on arrival, divided by fuel flow, in hours.
Why is my ETP before halfway?
That happens with a tailwind outbound. If you expected a headwind, check that O and H are not swapped.