Power. 747 can haul an immense load. Also, the 747 can fly at Mach 0.92, nearly 700 mph.
When president Bush was returning to Washington DC on 9/11, the F16s escorting him had to request that Air Force 1 SLOW down a bit because the F16s could not keep up without going into afterburner.
747 is still the “cadillac” of airframes.
“...747 is still the “cadillac” of airframes....”
Yes, she is quite a bird. A great ship. And given the purposes of Air Force One, the requirement for four engines makes a lot of sense. In past years, spent many hours on them flying back and forth to the Orient and Europe. I guess the A380 would be overkill....(chuckle)