Originally Posted by
ExSp33db1rd
That's the optimistic view - what happens when you are WAY beyond your PNR - at which point everything was on plan - and now have no option but to continue into unforecast increasing headwind.
That is what reserve fuel is for. The bottom line is as you are approaching the PNR you have to have your planned reserve fuel at destination. If you don't because the head wind component have not decreased as forecast then you have to turn around. This only works with a weather pattern that gives you strong headwinds to start but which are forecast to diminish throughout the trip.
You would have to be out of your mind to takeoff with a forecast increasing headwind along your route of flight.