Aircraft cruise speed

As far as I know, all aircraft can go more than 330 knots or mach 0.5 But for some reason the higher you go up, the bigger the speed restriction. The airspeed restriction starts increasing at 28,000 feet When you get to 38,000 feet it’s about 250 knots. Maybe I am miss understanding something, but that just sounds ridiculous.

IAS. Indicated airspeed. Less air=less pressure in the tubes. Which is why you don’t use that all to much. The higher you go, the more restriction. The restriction is for airlines which have a max cruise of .9-94 on some business jets. If you’re in a wide-body jet 777 cruise is .84 which is 315kts roughly. 300 kts is mach .8 btw not .5
Your IAS may be like 250-260 at cruise. But i promise you, if you set your speed to mach .84 it’ll read .84 where it shows mach speed. Further more, your ground speed would be 400-600 kts.

What i first said was probably way off


@Alphadog4646 did a nice job hitting on the key points. This video goes into more detail if you’re interested:


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