You’ve probably heard stories about passengers trying to open a door in mid-flight.

The bad news is the rest of the passengers can get quite a scare watching someone have a breakdown and go for the exit door.

The good news is it’s impossible to get the door open while the plane is in flight.

The first reason is that plane doors are mechanically latched closed, and only the pilot has the controls to unlock them. Next time you’re in a plane making a landing, listen for the pilot’s announcement, “doors to manual.” At that point – and only at that point – the unlocking control is undone, allowing someone else to open the doors.

Pilot Patrick Smith, on his blog AskThePilot, explains that the reason why the doors can be opened once the plane is on the ground is in case of an emergency evacuation. A similar announcement, “disarm doors,” refers to the function of deploying slides, if needed. “Those slides can unfurl with enough force to kill a person, and you don’t want them billowing onto the jet bridge or into a catering truck.”

So, yes. If the plane is on the ground, it is possible for a passenger to get a door open.

But, in flight, it is literally impossible – and that’s because of reason #2…

Air pressure. Planes are pressurized on the inside during flights because of the lack of oxygen at typical cruising altitudes. We can’t breathe up there without pumped-in air.

The air that keeps the cabin pressurized so we can breathe also seals the doors shut. The doors actually fit the plane-like plugs. To give you an idea of the amount of pressure keeping cabin doors sealed, at usual cruising altitude there will be eight pounds of pressure per square inch of the plane’s interior. This works out to 1,100 pounds pushing against every square foot of door.

Meaning no one is opening any airplane door while it’s flying. So get back to worrying about something more likely to happen: your luggage getting lost.