1> Only one person survived the plane crash.
2> Only one person survived in the plane crash. Are both sentences correct?
3> How many people did survive in the plane crash? How to change it to interrogative?
"How many people survived the plane crash?" is the usual question.
But consider this dialogue:
Tom: I hear that 50 people survived the plane crash.
Mona: You are wrong!
Tom: Oh, yeah? Well, since you always know everything, how many people did survive the plane crash?
Here's another example:
Tom: I hear that 50 people came to the party.
Mona: You are wrong.
Tom: Oh, yeah? Well, how many people did come to the party?