Used to be a very regular player of infinite flight and have returned after a nearly 2 year absence.
I am using the same device, iPad mini 32gb.
The game keeps crashing, often before pushback when I am making a flight plan. Or a couple of times during pushback.
I have graphic settings on medium.
I have cleared scenery cache.
Updated IOS and Infinite flight.
Restarted device.
I have just over 16gb out of 32gb free storage.
Uninstall the app possibly. Do a full power down of your device and then go from there. Clear all your replays before your flight. I think these might help
Edit: @BinaryChess seeing how OP states they have updated IOS and infinite flight assuming his IOS is updated to the latest version as well as infinite flights is.