How do we breathe on commercial airplanes? If humans breathe out carbon dioxide then shouldn’t we run out of breathable oxygen at some point?

Question

Might be a silly question, but I’ve always wondered how this works.

In: Other

Answer 1

Many aircraft also implement liquid oxygen (LOX) because high altitudes often lack enough oxygen to support life, or I guess consciousness.

Edit: I just reread what I wrote and I sound like an idiot, so to clarify the lox is primarily used for life support and not the main source of oxygen. There is oxygen at commercial heights, the air is just thinner and that’s why they pressurize aircraft.