[kortilla]

Air isn’t recirculated on an airplane. It’s continually brought in from outside the aircraft

[helloplanets]

50% is recirculated, 50% is from the outside. Before the 80's it was 100% from the outside, though.

[ses1984]

That statistic doesn’t mean much.

The question is how long does it take for all the air in the plane to be replaced.