And you have 15 seconds to get that oxygen mask on your face
At 36,000ft, the air is freezing. Like, -80F freezing. But don’t worry, you’ll only feel the frostbite for about 15 seconds before passing out from hypoxia, assuming you didn't get your oxygen mask on. Also, anyone who ignored the "fasten seatbelt" sign will, just like in the movies, get sucked out of the plane in seconds.
Pilots will try and get to a safe 10,000ft ASAP
Gradual depressurization is just as bad, as oxygen masks only have enough oxygen for a limited amount of time. Once that runs out, passengers become sluggish and fall unconscious. Before that happens, though, the pilots -- wearing more advanced rubber oxygen masks -- will try to bring the plane to a safe and breathable altitude of 10,000ft.
Thanks to D.B. Cooper, planes are actually safer
At this point, you might be like: “But what about D.B. Cooper, didn’t he jump out of a plane and make off with $200k?" Well, good point. However, Cooper had forced the pilot to depressurize the cabin first, effectively unplugging the emergency exit before jumping out with a parachute. Since then, the FAA has forced airplane manufacturers to install something called the “Cooper Vane," which prevents the doors from opening while the aircraft is in flight.