Originally Posted by
dilanesp
To add one more point on the widebodies, when I started flying, it was common to see 747's, DC-10's, and L1011's flying LA-NY and SFO-NY, on United TWA, American, Continental, and Pan Am.
It isn't as though all that demand ever disappeared. It's just that a lot of airlines switched to smaller planes for frequency reasons and to ensure higher loads.
It still makes a lot of sense to fly big planes on those routes.
They switched because they could. IIRC, the 757/767 were the first twin engine aircraft that could do trancons. Even the 737-300 couldn’t do it westbound at full load.