A very interesting column from Patrick Smith discusses “What if my seatmate tries to open the cabin door at 37,000 feet?” This is well-worth the very short ad before access, especially for anyone who flies.
During flight none of these doors can be opened, for the simple reason that cabin pressure won’t allow it. Think of an aircraft door as a drain plug, fixed in place by the interior pressure. With very few exceptions, aircraft doors open inward. Some retract upward into the ceiling; others swing outward or downward against the fuselage; but they all open inward first, and not even the most musclebound human will overcome the hundreds of pounds of pressure holding them shut. At a typical cruising altitude, as many as 8 pounds of pressure are pushing against every square inch of interior fuselage. That’s 1,152 pounds of weight against each square foot of door. Flying at low altitudes, where cabin-pressure levels are lower, even a differential of 2 pounds per square inch is still more than anyone can displace — even after six cups of coffee and the frustration that comes with sitting behind a shrieking infant for five hours.