Yes. At high (sub sonic) speed and high altitude, you get close enough to the speed of sound that this starts to matter a lot. https://aviation.stackexchange.c

Yes. At high (sub sonic) speed and high altitude, you get close enough to the speed of sound that this starts to matter a lot. https://aviation.stackexchange.com/questions/35408/what-is-the-reason-for-changing-the-speed-reference-ias-or-mach-number-with-al https://aviation.stackexchange.com/questions/35408/what-is-t...