Airplanes get an unlimited supply of oxygen from the surrounding air. Outside air is supplied from the compressor stage of turbine engines and is passed through a bunch of machinery to ultimately be piped into the cabin for passengers. read more
The oxygen inside an airplane comes from atmosphere only. You must know, there are two types of airplane cabins; pressurised and unpressurised. In an unpressurised one, the airplane's cabin is through to the atmosphere. read more
Normal oxygen found on airplanes in the cabin is just air from the ground that is pressurized. However, air coming from emergency masks is from a storage tank or oxygen generator in the cargo hold or above the seats. read more
Airplanes use oxygen generators, otherwise known as "oxygen candles." These are chemicals that, when burned, release oxygen as a gas. Any extra chemicals get filtered out when the oxygen goes through to your mask, and the entire thing keeps going until it burns down. read more