One reason the 747 has had such a long life is that when it was developed, the expectation was that it would soon be replaced by faster supersonic aircraft, so it was designed to be easily re-purposed/retrofitted to serve as a cargo aircraft --- that said, despite its vast cargo capacity, since it was the last major aircraft designed using pen and paper, if one were to print out a compleat set of blueprints/specifications and try to load them into one, it would probably be too heavy to take off.

It really was remarkable to fly in, esp. if one was fortunate enough to sit in the front rows of seats which had the wrap-around windows, or to be admitted to the cockpit as was often done for children when I flew from Japan to the U.S. on one (somewhere in my stuff is a set of plastic Pan Am wings which the pilot gave me).