NIGHT76 on the ground at Wright Patterson AFB, OH after a speed run from Offutt AFB, NE.
PF is also commercial pilot, but not 747 rated, so did some checking and the old girl was being pushed close the limits. Mmo (max mach no. is .9) and the ground speed indicated was at one point 556kts (640mph).
Checking winds aloft at that location for 500mb (18,000') showed a tailwind of about 50kts. So pushing close to 500kts TAS. Max cruise is .83 mach or 495kts.
They were going as fast as that bird could go.
Notice it never climbed above than 19K and a trip that long would've been planned to get high where the winds aloft and density are favorable. They were in a big, big hurry.