Do you often drink bottled water during flights? Then you must have noticed that the bottles deformed once the plane returned safely to the ground. It looks like all the air has been sucked out of the plastic bottle. how is that possible?

Plastic bottle scratches due to pressure difference

A plastic bottle that you drink from during flight gets deformed during landing. But the water bottle you never open during the flight won’t. Not even if I took her half drunk on the plane.

The change in the shape of the bottle is due to the air pressure in the aircraft. It is not the same throughout the flight. At takeoff, the aircraft has an atmospheric pressure similar to that of air at sea level, about 101 kPa. At normal flying altitude, the air pressure inside is much lower, about 75.3 kPa. Outside the plane, the air pressure is much lower, but people don’t like it. During descent, the air pressure rises again to 101 kPa.

If you open a beverage bottle mid-flight and take a few sips from it, the liquid in the bottle will be replaced by air at relatively low air pressure. If you screw the cap on the bottle back on, the contents of the bottle will maintain the same air pressure.

Once the plane lands, the air pressure in the cabin is higher than the air pressure in the bottle. This is why the water bottle breaks.

This can cause the shampoo bottle to leak

On the contrary, during takeoff, the cap of a half-empty bottle can explode. This is because the air pressure inside the bottle remains at ground level, while the air pressure outside the bottle decreases.

Not only water bottles fall prey to changes in air pressure. Sometimes your shampoo or conditioner bottle can also be the problem. Did you notice after your flight that your shampoo started leaking in your bag? Then it is probably not because the ground staff was rude to your luggage, but because the cover was loose during take off.

Read also: Why does your phone have to be in airplane mode during a flight?, What exactly is the disruption? What does a pilot do during a long flight?