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Answer by Ron Wagner, airline pilot and former USAF aviator:
Sure, no problem at all, if you’re strong enough to pull sideways with 3 to 4 tons of force.
Every once in a while back in my airline days, a young flight attendant would breathlessly race into the cockpit to warn us that a guy in an emergency exit row was trying to open the door. She’d ordered him to stop, but he just kept trying. Now she needed one of us to come back and stop him. We just laughed and told her to ignore him. Because it is funny.
At cruise altitude, the average exit hatch has about 3 to 4 tons of pressure holding it in place. Even on the ground, once the pressurization is turned on, there’s maybe 400 to 800 pounds of pressure. Yes, airliners pressurize a bit on the ground, which prevents pressure bumps that would pop your eardrums during takeoff. It’s less than 1 psi, but multiply that by hundreds of square inches and you’ll see that even if we went back to try to stop the guy, even on the ground, if he was strong enough to pull it out, we weren’t going to stop him.
Now, escape hatches are different from the main doors and are pretty easy to design because since they’re removed from the inside, they’re simple plugs, and pressurization makes them essentially impossible to remove. The main doors do indeed open outward. Why don’t they blow out?
Airliner doors are ingeniously designed. Few people realize it, but it’s some really excellent engineering. Next time you’re boarding a Boeing, take a good look at the mechanism. Upon closing, the door swings inside the cabin and then nestles outward into a frame where the door becomes a plug. They’re called plug doors. In aviation, you always want physics to work in your favor, so cabin doors use physics to remain in place rather than fighting physics with some massive locking mechanism.
Without this design, eventually with daily use on tens of thousands of planes, over decades, one of these locking mechanisms would eventually break and a door would open in flight. I’ve never heard of a plug-type cabin door opening in flight.
Unfortunately, designers have not always used that principle on all aircraft doors. The doors on the lower baggage bins on a DC-10 are a tragic example. They used a locking mechanism, something akin to a bank vault. Very strong, but something that must not deteriorate with thousands of uses by baggage handlers. Sadly, a couple of them failed.
One such example was the crash of Turkish Airlines Flight 981. The rear cargo door blew out with such force that the entire aircraft frame buckled. (MD never built planes as strong as Boeing.) The buckled floors left the control cables under the floor hanging slack. The pilots’ yokes in the cockpit were just loose and floppy. All they could do was let everyone pray while they watched the plane slowly go out of control and crash.
This crash resulted in a complete redesign of the locking mechanism, and no more DC-10 nor MD-11 cargo doors have blown out. But those accidents, combined with others caused by sloppy design, eventually caused the DC-10s to cease passenger operations. They now only carry freight.
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