"Nightmare at 20,000 Feet."

Arguably one of the most iconic episodes

of the show ever made,

it stars William Shatner as a:

Clip: Portrait of a frightened man:

Mr. Robert Wilson.

Narrator: Bob sees a gremlin on the wing of the plane

and decides the only possible solution to the problem

is to steal the air marshal's gun, open the emergency exit,

and shoot the thing.

Clearly, this scene is complete fantasy.

And I'm not talking about the gremlin.

There are a couple of reasons

why you can't open an airplane door mid-flight.

The first being: It's locked.

But there's another big factor

that "The Twilight Zone" seems to ignore,

and that's physics.

Let's consult our first completely reliable source,

the episode's IMDb "Goofs" page.

It says the plane Shatner's flying in

is either a twin-engined Convair

or a four-engined Douglas DC-6 or DC-7.

All of which would have been pressurized.

The higher a plane flies,

the lower the air pressure outside.

And the lower the air pressure, the harder it is to breathe.

That's because the air is thinner the higher you go.

The molecules are literally farther apart.

So there are fewer oxygen molecules

in every breath you breathe

and less pressure diffusing that oxygen

into your bloodstream.

Over 18,000 feet above sea level,

and our bodies just aren't able to absorb enough

to keep us functioning.

That's why planes are pressurized to mimic conditions

about 8,000 feet above sea level.

It's a nice middle ground that lowers

the oxygen in our blood by only about 4%,

which is not enough to really affect how we function.

Modern airlines fly at about 36,000 feet above sea level.

If they weren't pressurized, it would cause delirium

in seconds and knock you out in under a minute.

And the difference between the inside of the plane

and the outside can be huge.

Which is exactly where the doors come in.

Inside the cabin, 8 pounds of pressure

push against every square inch of surface area.

The typical passenger door is about 6 feet tall

by 3 1/2 feet wide.

So we're looking at more than 24,000 pounds of pressure

bearing down on that exit.

The strongest man alive can deadlift only 1,102 pounds.

"But wait!" you scream at your computer screen.

"This nightmare was at 20,000 feet, not 36,000.

The pressure would be lower!"

You're right, but there's no need to yell.

Clip: Keep your voice down.

Bob: I'm sorry, I'm sorry.

Narrator: The pressure would be lower,

but still too much for a person to overcome,

even William Shatner.

And the door flying out into the inky black?

Practically impossible on a modern plane.

Most passenger doors are tapered,

the inner edge being wider than the outer.

It's called a plug door, and it basically acts

like a bathtub-drain stopper,

corking the hole without falling through.

But what if someone on your plane

had Shatner's superhuman strength?

It could cause something called "explosive decompression."

And it's the one thing "The Twilight Zone"

got mostly right.

During an Aloha Airlines flight in 1988,

a piece of the fuselage tore loose at 24,000 feet,

leaving "blue sky where the first-class ceiling had been,"

according to the captain.

The chief flight attendant was instantly

sucked out of the plane through that gaping hole.

Explosive decompression happens infrequently,

but it does happen.

A rip in the plane wall, a window cracks,

it doesn't matter the cause.

The huge pressure difference creates a vacuum

capable of shooting anything up to 1,000 pounds

out into the sky.

And that vacuum effect would last until

the pressure inside the cabin

matched the pressure outside.

So Shatner made a good call buckling himself in

before opening that emergency exit.

If you don't live in the Twilight Zone,

your chances of pulling open an airplane door mid-flight

are just as good as seeing a gremlin on the wing.

So the next time you start getting nervous about it,

just remind yourself:

Bob: I'm gonna be all right.