Due to the different pressure inside and outside the bag it sometimes forces it to expand and even burst midflight. In the event of an aircraft gaining altitude, the gas inside the chip bag will expand as the atmospheric pressure (the pressure outside the bag) decreases.

When a bag of crisps (chips) is taken on a plane, it typically puffs up and expands significantly as the aircraft reaches cruising altitude. This phenomenon is a practical demonstration of Boyle’s Law, which states that the volume of a gas is inversely proportional to its pressure. At sea level, the air pressure inside and outside the bag is equal. However, while airplane cabins are pressurized, they are usually only pressurized to an equivalent altitude of 6,000 to 8,000 feet, where the air is thinner. As the external cabin pressure drops, the air trapped inside the sealed bag pushes outward with greater force, causing the bag to inflate like a small balloon. In rare cases, if the seal is weak or the pressure change is rapid, the bag may even pop or burst.