Point of No Return ?
 

Does anyone know when we will use PNR concept for Flight Planning ?
Did your Airline use PNR for planning flight ?

I believe our Flight Planning people use an ETP (Equal Time Point). basically the same thing as a PNR.

If you are operating VFR, without an alternate, and without enough fuel to divert to your departure point, then you should calculate your PNR. In the calculation, your endurance should not include fuel reserves.

The speeds used are, of course, groundspeeds, i.e. dependent on the actual wind.

ETP/CP and PNRs are very different.

Equi-Time Point / Critical point is a time based consideration, the point along your FPT where you are exactly x minutes to your origin and x minutes to your destination. There are many variations of this though, whether it be a normal ops , depressurization or Engine out situation.

PNR is a fuel based consideration, it is the last point on the FPT at which you can safely return to your destination.

Aircraft operate with PNRs or LPSDs generally on routes where they push their range or push there tank capacity and are unable to carry additional fuel to allow for alternates or holding due WX etc. If the forecast for arrival is below the minima by the time the a/c reaches its PNR or LPSD it is basically forced to divert or return to origin.

Quite common for A320s or 737 operating 5 hour legs to relatively remote aerodromes.

Interesting question. I had to dispatch to Easter Island once, isolated without alternate in the calculation, and they were requiring info about our PNR. We decided to give our ETP instead as no way we could accept a PNR as a final decision point. I can only imagine using it for ferry flights to remote overwater places with limited range aircrafts?