landroger:
I can see from his and the other answers that the 767 has the power reserve to punch it along faster, but it's intrinsic aerodynamics don't want to go that fast. Now, I have always understood that the B747, in most of its forms, was and, so far as I know, still is the fastest subsonic airliner in the business?
No, that title goes to the Convair 990.
The 707s I flew had a planned cruise of Mach 0.86 and we could easily do Mach 0.89. This was when jet fuel was 21 to 27 cents per gallon.