Because I think you should know these things: We've all seen countless airline hijacker movies or movies like "Airforce One" where there's gunplay in an airliner, flying at altitude. Then, some wise guy who can't aim shoots and the bullet goes into and then out of the cabin wall, causing a huge sucking, whooshing sound, followed by flying paper, and then flying people out of a now-gaping hole. And you know the hero will just manage to snag an errant seatbelt at the last moment before he tumbles down 35,000 feet himself.
Come on people, you know you've seen this!
Anyway, there's no way it could happen. So, you're okay; fire away.