On the subject of indicated airspeed, does the mach number have the same meaning? That is, if the aircraft had reached an indicated airspeed of Mach 1, would they break the sound barrier and experience a sonic boom?
I think you have some confusion about indicated airspeed - it's used because it provides pilots with predictable information about how the plane will react, it's not indicative of the actual speed of the plane: https://en.wikipedia.org/wiki/Indicated_airspeed
They were truly at 0.9 mach, had they increased speed by 11% they would have broken the sound barrier, well before the indicated air speed would have read a >mach 1 number.
