Interesting topic. In my thirty-five years of air travel I recall the following:
Eastern, Western, Trans Texas, Texas International, Braniff, Southern, Ozark, Piedmont, People Express, Pan Am, Allegheny, Republic, Western Pacific, Mark Air, Reeves Aleutian, TWA, BOAC, National, PSA, Reno, Hughes, Canadian Pacific, Mid Pacific, Wein Air.
I suspect there may be a couple of more that don't readily come to mind.