An airline thats strong and making money is a pretty difficult target. Theres no telling what airlines will be around in 20 years. All it takes is a little bit of bad PR to crush an airline. Just ask TWA and Pan Am which is why neither one of those 2 names are even used today. Probably one of the only reasons UA and AA and their names survived 9/11 was all the money the government gave them to keep them running
Delta only bought Pan Am's European (non-London) routes and rights to use the Pan Am name for a short period, which they didn't use.
However, with American's takeover of TWA, they decided that American was a better name. I disagree but do almost see the logic of it as the American name isn't bad.
With Delta and Western, Delta was the stronger name. So was US Airways and America West.