Speed of jet planes in mph?

Answer 1

Some modern jet aircraft have enough power to hover so the low speed would be zero mph - fastest known speed, by the SR-71 Blackbird, was 2070.101 mph but it's quite possible the USA military has broken that but hasn't said so.

If you would like to convert speeds yourself from knots:

1 knot = 1.15 mph so multiply the knots by 1.15 for the mph sped

It's quite possible scramjets have beat that record speed but scramets are a hybrid engine and not a true jet As a rule of thumb, commcial jets crue at somehere between Mah .78 and Mach .85, which, at normal cruising altitudes and temperatures, would be in the 510 to 565 miles per hour range. Remember, however, that aircraft speeds are normally True Air Speeds (through the air) and so if you're trying to figure out how long it will take to fly somewhere, you will need to add a computation for the wind, which will give you ground speed, or speed across the ground.