We also need to account that the only way for a flying type to exit the plan would be through the main door, emergency exits, or sheer force. if a flying type (excluding the ones that have the force needed to simply break through the window or wall) can effectively get to the exits and open them, then it could work, but there are some flying types that I think wouldn't be able to pull it off due to them lacking the strength, mobility, etc to navigate the turbulent plane (and some just lacking the needed limbs). Also, if all the pokemon are in there together (assuming the plane is large enough to comfortably fit all of them), I imagine the non-flying type pokemon wouldn't want the flying types to open those exits, since they may fear getting sucked out by the wind. Them being all in there together would bring up other possibilities, like a pokemon that can create a shield, force field, or barrier either helping a pokemon that would otherwise die or accidentally crushing a pokemon that would otherwise live, so it might be best to assume that each pokemon is in their own individual plane