Originally Posted by
n5296s
I was always under the impression that the airflow in flight tended to keep the doors shut rather than open - though I've never tried to open them.
152 doors hang open an inch or so in the slipstream, and it's part of the forced landing preparation to open the doors before touchdown (so you don't get burnt to death through lack of being able to force open a jammed bent door).
The same is officially true of 172 doors but, unlike in a 152, I haven't actually had a 172 door come spontaneously open on me, so I don't have any personal experience of flying them with a door open.