> after all some normal passenger airports are a few thousand feet above sea level
The parent commenter is referring to airports at high elevations. They mean to say that opening the doors is almost impossible at cruising altitude, which is far above any airports. Hence, the doors can only be opened when not on the ground during early ascent and late descent.
The parent commenter is referring to airports at high elevations. They mean to say that opening the doors is almost impossible at cruising altitude, which is far above any airports. Hence, the doors can only be opened when not on the ground during early ascent and late descent.
I hope my explanation makes sense.