I was wondering why airlines who bought the 737-300 didn't go with the 737-400 as well. USAirways and Alaska (and Carnival when it existed) are the only U.S. airlines to have it that I know of.
United, Continental, and Southwest have the -300 and the -500, but why didn't they take the -400, too??
A310/319/320/321/333, ARJ, BN2, B722/73S/733/734/735/73G/738/739/744/757/753/767/763/764/777, CR1/2/7/9, DH6, 328, EM2/ERJ/E70/E75/E90, F28/100, J31, L10/12/15, DC9/D93/D94/D95/M80/M88/M90/D10, SF3, SST