Originally Posted by Lonewolf
Just out of curiosity, is this a boundary layer phenomenon?
Stall always involves the boundary layer. It wouldn't occur in friction-less flow, but there wouldn't be any lift either. To comment on the Mach involved - I noted a while back that alpha-max is defined by low-speed stall at more or less constant AoA up to M=0,275, and is defined by Mach-related buffet above that M. In AF447 stall occurred at about M=0,6 (2:11:06, 185 kCAS at FL375).