flew into a flock of Canadian geese

shortly after taking off from New York's LaGuardia Airport.

The plane lost all engine power while flying over Manhattan.

Their options?

Attempt to land on the Hudson River

or crash into one of the densest cities in the US.

Clip: I don't know. I think he said he was

going in the Hudson.

Narrator: Thanks to clear conditions, expert piloting,

and a quick response from emergency crews,

all 150 passengers survived.

You may have heard this story before,

but it's not the only time

something like this has happened.

And despite that success,

landing a plane on the water is extremely dangerous.

Ditching is a controlled emergency landing on water.

It can be caused by almost anything,

but usually it's because of engine failure

or running out of fuel.

Pilots only decide to ditch an aircraft

when there is no better alternative.

Despite the difficulty,

pilots don't undergo extensive training on ditching.

Chesley Sullenberger, the pilot of US Airways Flight 1549,

told The Telegraph in 2018:

Carolina Anderson: You really don't practice,

not even in the airplane

or in the simulator,

but most airlines will cover it in training.

But it's not something

that is mandated for every airplane.

Narrator: That's Carolina Anderson.

She's an associate professor of aeronautical science

at Embry-Riddle Aeronautical University.

Anderson pointed out that it's rare

to have to ditch an airplane.

Anderson: It's not something that is very common.

You see them in smaller airplanes more often,

in big airliners not very often.

Narrator: Planes are usually tested using simulations,

rather than actual bodies of water.

The aircraft needs to float long enough

for passengers to evacuate.

But pilots have to worry about more than just the plane.

Unlike landing on a runway, there are a lot of variables

that are out of the pilot's control.

The most obvious is the waves.

The larger the waves, the more dangerous the landing.

Pilots try to land parallel to the waves,

instead of across them,

so the waves don't push the plane around,

which could cause damage to the plane,

injure passengers, and make evacuating more difficult.

Like in 1956, when Pan Am Flight 6 had to ditch

in the Pacific between Honolulu and San Francisco.

Upon landing, a wing hit a swell,

rotating the plane 180 degrees,

damaging the nose, and breaking off the tail.

Luckily, everyone survived.

While ditching, pilots have to keep the wings level

and maintain an incoming angle

that's not too steep to prevent a hard impact.

Inside the plane, the passengers will be told

to brace for impact.

And anything loose in the cabin will need to be tied down.

Another huge factor is the weather.

Clear conditions give a pilot better control

over the aircraft and increased visibility.

Pilots balance all of these variables

in order to prevent the aircraft from breaking apart.

If a plane breaks upon impact,

there is a huge risk of flooding.

Anderson: You're not going to float for very long,

and if you land too hard, the chances of breaking it

are very high because water is going to get in

and it's going to start sinking.

Narrator: And if a plane flips over,

flooding will occur much faster.

Anderson: Basically, you want to touch down as slow

and as soft as possible.

If the airplane has retractable landing gear,

you want the gear to be up

and you want the flaps to be completely down.

Narrator: If the landing is successful,

the next step is getting everyone off the plane.

Which has to happen quickly,

since the Federal Aviation Administration requires planes

to be able to be evacuated within 90 seconds.

Thankfully, modern planes are equipped

with a bunch of safety features to help

passengers if an aircraft is ditched.

Commercial planes use rafts and flotation devices

like life preservers.

They also come with flares and emergency radios.

Airplanes are designed so that a water landing

won't cause immediate harm to passengers.

Many ditching-related deaths are from drowning,

not the impact.

But don't let this discourage you from flying.

Forced water landings are unlikely to happen,

especially on a commercial flight.

Whenever flying, you should listen

to safety instructions carefully.

And always remain calm.