[jmward01]

if you stay subsonic. I hear the U-2 has like 1-2kt of leeway when it is at its max altitude because if it went faster it would be supersonic but any slower and it would fall out of the sky.

[tonyarkles]

To the point where, if you turned too hard, you could stall one wing tip while Mach buffeting the other.

[FredPret]

Obligatory plug for the excellent book Skunk Works by its former director, Ben Rich.

[sidnb13]

+1, immensely satisfying read for any aviation nut