[dragonwriter]

> Funnily enough the SR71 at Mach 3.5 had a better mpg than a Boeing 747 below Mach 1.

The SR-71 had a maximum takeoff weight of 140,000lbs.

The 747 has a maximum takeoff weight of 735,000-910,000 lbs, depending on model.

That helps quite a bit for the former using less fuel per mile.

[thfuran]

And a considerably higher percentage of the 747's weight is passenger/cargo as well.