Here's a really funny one: I used to think that when you got up on a plane to go to the loo, the pilot would stop the plane in mid-air until you're out again.
A childhood belief about aeroplanes

others believed things like this
- My friend's sister used to think the auto pilot on a plane was an inflatable man like the one in Airplane!— Richard Davies
- I used to believe in the plane there were birds to make it fly— laura 401
- I used to believe that Florida was up in the clouds and that's why we had to take a plane to get there.Anon
- if heavy people went on a plane i thought that it would tip over.— michael hague
- I thought that Heaven was literally up in the sky and you could fly there in a plane— Nate
- i used to believe if i was in a plane, i'd be able to reach out, grab part of a cloud and eat it— BOXXXY