Once the cruising speed was fixed safely below the speed of sound, almost no choice was left the designer. At reasonable finesse, the wing loading is fixed by the speed, given the altitude. The cold, thin stratosphere, some 65 degrees below zero Fahrenheit, is entered about six miles high, and the temperature falls only slowly much beyond that. Engines like cold air, but lift depends on the mass of air deflected downward. A universal trend runs from wren to jumbo jet that neatly relates wing loading to speed at a given air density.
Wings grow big as their load increases.
The 747, its lift 15 times its drag, is no bigger than it should be. Only by compromise. It would fly with disproportionately bigger, dearer, draggy wings. Swifts and swallows fold their wings at top speeds to cut drag, but so far only expensive military craft follow their example and not airliners, even though at landing, its fuel gone, the 747 is much lighter and needs less wing area than it does at takeoff. A much larger plane meets still more troubles.