Every now and then, we hear about those disconcerting incidents of passengers trying to open a plane door during a flight. These attempts are usually halted, promptly, by crew members. But the question still remains: Can plane doors actually be opened while the aircraft is thousands of feet up in the sky?

The short answer is you’d have to be very, very strong to do it — so strong that it’s basically impossible.

“The likelihood of a door being ripped open by a human being is very low,” said Dennis Tajer, a pilot who’s been working for American Airlines for 25 years. “Airplanes are designed for that not to happen.”

The inside of plane cabins are set to have a much higher pressure than the air outside planes, with a difference of eight pounds per square inch. Common passenger doors are about 6 feet tall by 3.5 feet wide. This means that to open the door, one would need to overcome more than 24,000 pounds of pressure — about the weight of six cars or 20 polar bears. Most airliners also use “plug-type” doors that fit tightly onto the door frame.

“The higher interior pressurization actually seals the door to the frame,” said Douglas Moss, a pilot for United Airlines for 20 years.

Additionally, there are lock bolts that hold the doors together, and permission from the cockpit is required to disable them, Tajer said. These bolts are often located deep inside the structure of the aircraft, and cannot be destroyed by force at the surface.

And even if a passenger did somehow manage to crack open a door, it doesn’t necessarily mean it’s time to panic. It could get loud, humid and foggy, and the temperature might drop significantly, according to Moss. As Tajer put it: “It would not be good, but it would not be dangerous.”

This doesn’t mean attempts to open a door while a plane is in flight should be taken lightly. Far from it, pilots say. A passenger who tries to open the door is demonstrating “an unstable mental condition,” Moss said, advising people to try and subdue the person in such situations. “No one can be certain what other dangerous acts they may attempt.”