Popular Mechanics offers some tips:
You have a late night and an early flight. Not long after takeoff, you drift to sleep. Suddenly, you’re wide awake. There’s cold air rushing everywhere, and sound. Intense, horrible sound. Where am I?, you think. Where’s the plane?
You’re 6 miles up. You’re alone. You’re falling.
Things are bad. But now’s the time to focus on the good news. (Yes, it goes beyond surviving the destruction of your aircraft.) Although gravity is against you, another force is working in your favor: time. Believe it or not, you’re better off up here than if you’d slipped from the balcony of your high-rise hotel room after one too many drinks last night.
Or at least you will be. Oxygen is scarce at these heights. By now, hypoxia is starting to set in. You’ll be unconscious soon, and you’ll cannonball at least a mile before waking up again. When that happens, remember what you are about to read. The ground, after all, is your next destination.
Granted, the odds of surviving a 6-mile plummet are extraordinarily slim, but at this point you’ve got nothing to lose by understanding your situation. There are two ways to fall out of a plane...