Many people plan summer holidays around the world as the year progresses.

When on a plane, people may look out the window and notice small holes. They may wonder what these holes are for.

A pilot explained that the holes help control air pressure inside the plane. Plane windows have three layers.

The three layers and holes make the plane safer for passengers. These holes are called 'breather holes' or 'bleed holes'.

A YouTube user, Mentour Pilot, explained that the bleeder holes are in the middle layer of the plane windows.

The outer layer handles impact and pressure difference. There is air between the outer and middle layers.

A breather hole is shown in a close-up photo.

The bleed holes control air pressure across the layers. They prevent forces from building up between the layers.

The hole allows air to flow through and relieve pressure difference.

The layer closest to passengers does not have a hole. This layer is designed to let air flow around it.

Plane windows have holes to reduce moisture build-up.

The holes make it hard for moisture to get trapped and fog up the window.

The pilot shared secrets about flying.

Some flight attendants shared information about airline secrets. They explained why they greet passengers.

A flight attendant explained why they always greet passengers.

A flight attendant said greeting passengers is also a way to check their health. It is a safety evaluation before takeoff.

The flight attendant greets passengers to check if they are too drunk or sick to fly.