During WWII a plane (bomber plane maybe?) crashes in the middle of nowhere. Some die but a lot of the soldiers survived the crash. As they figure out how to survive while they wait to be rescued weird things start to happen. No one can leave the crash area. Then the bodies of the dead start disappearing. Then the survivors start to disappear.
The twist is revealed when scenes of modern times show that no one survived the crash and they are disappearing because their bodies are being taken away from the crash and finally find peace.
“Sole Survivor” (1970)
https://www.imdb.com/title/tt0065007/
https://en.wikipedia.org/wiki/Sole_Survivor_(1970_film)
You can watch the complete movie on YouTube here:
I am pretty sure that this is your movie. If you agree, then please select my answer as Best Answer, there is an option for that.