What is the cruising speed of a jet?

According to Boeing, the cruising speed of their jets are as follows:

MD 90 -- Mach 0.76, or approximately 500 mph (812 km/hr)

707 -- 550 mph (885 km/h)

727 -- 570 to 605 mph (890 to 965 km/h)

737 -- Mach 0.82, or approximately 550 mph (885 km/hr)