I can not find anything in the rules that state that AAA guns, or other planes/Aircrafts, stops one of your own aircraft from flying over them.

is it true that if you fly through a hostile country, then there is nothing to prevent this, or CAN prevent this?

Thanks! It helps

Russia start not in war with the Axis and cannot attack axis unless attacked first… But does attacking a Neutral Pro Axis nation (as Finland) count as an attack at Axis? or is this move legal?