On top of a plane wing, there is a yellow hook, often with two holes in it.

The reason for this strange contraption is in case of an emergency situation.

The hooks are needed in case the plane needs to make a landing on water, The Sun reports.

Ropes are attached to the hooks to make it easier for passengers to get out of the cabin.

Airline pilot and YouTuber Captain Joe explained the hooks in a video.

“In case of an emergency landing, let’s say on water, the flight attendants will want you to evacuate from the overwing exits,” he said.

“Once you’re at the door and you set foot onto the wing, you’re most likely going to fall because the surface will be wet and very slippery.”

He said the escape ropes could then be fastened to the door frame and the hook.

“Another rope is hooked up in the other hole leading towards the slide,” he continued.

“This little piece of metal was installed so that the escape rope can be attached, giving you a safer stand on the slippery surface on top of the wing.”

One of the most famous plane landings on water has now been named The Miracle on the Hudson.

Turned into a film featuring Tom Hanks, pilot Chesley Sullenberger was flying US Airways Flight 1549 on January 15, 2009, when both engines of the plane were struck by birds.

He was forced to land the plane on the Hudson River, and miraculously, all 155 people on-board survived.

An expert has revealed some other ways to improve your chances of surviving a plane crash.

This includes checking where the emergency exits are as well as removing anything from your pockets and wearing sensible shoes.

This story originally appeared on The Sun and is republished here with permission