The SR-71's "speeds" are not classified. You can even download the long ago declassified manual that says what the max mach number it can display is. The actu

The SR-71's "speeds" are not classified. You can even download the long ago declassified manual that says what the max mach number it can display is. The actual top speed might still be, if it is, it's probably because they don't actually know what it really is. There have been multiple pilots who have said they could pretty much keep giving it gas and it would keep going faster.