15 points
*
The FAA designates 18,000 ft to flight level 600, which is 60,000 ft above sea level, as class A airspace. Any aircraft needs explicit permission to enter class A, so that’s normally only when an airliner is climbing to cruising altitude, but it would also occur when a spacecraft is descending through 60,000 ft.
Other countries, I don’t know exactly, but they all function fairly similarly.
