I don't think a flight has ever had a crowd crush event.
The largest passenger plane is an Airbus A380 with a typical passenger capacity of 575. And that's split between two decks. Most crowd crush events involve twice that amount of people all heading the same direction while the people in front have nowhere to go. And most crowd crush events are a result of building code violations such as emergency exits that open inwards.
Planes don't really allow for crowd crushes to happen. Every person would have to be trying to get to the same emergency exit at the front of the plane, and if you're mid flight why would anybody be trying to get to any exit?
Just stay in your seat and it's highly improbable to be crushed to death.
Phone of Theseus