Might be up to at least 22 minutes depending on the jet.
We had some 767s (7ER for the wookiee) that would produce O2 for an extended period. In some mountainous terrain routes, you're not going to be able to descend from cruise to a breathable altitude for an longer time because of terrain.
We had some 767s (7ER for the wookiee) that would produce O2 for an extended period. In some mountainous terrain routes, you're not going to be able to descend from cruise to a breathable altitude for an longer time because of terrain.