Virtually every time I read about the Lockheed SR-71 (including other threads on this forum), I see that its speed record is listed as approximately 2193 mph. The same blurb will invariably say this is "about Mach 3.3".
But when I search for how fast Mach 1 is, the number that almost always comes up is 767 mph.
Now 767 * 3.3 comes out to 2531, well above 2193. If I take 2193 and divide it by 767, I get Mach 2.85
I doubt I've stumbled on something new here. So what am I missing? How can 2193 mph be Mach 3.3 when 767 mph is Mach 1?