What is the floor of Class A airspace?
Why →
Class A airspace begins at 18,000 feet MSL and extends to FL600 (60,000 feet MSL). sUAS operations under Part 107 are subject to a 400 ft AGL ceiling, so Class A airspace is generally not a practical concern, but pilots must know the boundaries.The trap →
10,000 ft is a common speed limit threshold in manned aviation; 12,500 ft is where some transponder requirements kick in. Neither is the Class A floor.SOURCE → FAA Aeronautical Information Manual (AIM) Chapter 3CHECKED APR 21ACS II.A.K1MED