I have flown more than 20 times with my pump and never experienced a problem.
I have never used “flight mode” on my pump ... in my many ambling through the pump menus, I have never found a “flight mode”.
Typically, flight mode is used in electronic items, like phones, to stop transmission of any signals which could affect the flight of the plane. Not to protect the electronic items.
Thinking of the atmosphere of the plane (e.g. maintaining air pressure), I cannot think of any think that could affect the dosage of the pump.
And, I don’t know of anything that would affect insulin potency during a flight which would affect anyone who injects insulin when they fly.
But I may be wrong ... it has happened before but don’t tell too many people!