I guess they figured that if you have to put a piano in coach, than maybe you shoud find a plane better suited to your needs. Plus these were bought when PanAm still ruled the international routes. Back then, American 747 users, put these planes on busy, domestic routes like JFK-LAX/SFO, and LAX-HNL. When CAB disintegrated, and airlines were able to freely choose their destinations, both domestically, and abroad. However, PanAm was still the premier airline to fly internationally, and the airlines realised that it was nearly impossible to fill these planes, and maintain profitable yields. By the time the PanAm empire crumbled, airlines other than Northwest (which had had it's Pacific empire carved out for decades by then), bagan to fill PanAm's shoes. But, PanAm collapsed after American got rid of their 747's. The MD-11's were already on order. Plus, PanAm got split up like this: Delta, got domestic, and European divisions, United got the Asia/Pacific divisions, and American got the Latin American divisions (where mighty PanAm got it's start!), plus LHR slots. As American and Delta didn't need to cover the distances that necessitated 747-400, they went for the MD-11. Plus Delta got PanAm's A310's. United, who got the Pacific rights, needed an aeroplane to cover PanAm's West Coast-Australia flights, plus other long range flights, like JFK-NRT. United got PanAm's 747's, L-1011's, and 747SP's. Northwest, having the largest trans-Pacific operation of any airline also needed an aeroplane to cover flights like Australia, and MSP-HKG.
So it really wasn't abandonment, but rather American realising they had an aeroplane they couldn't fly profitably. They found a better mate in the MD-11, and now the 777.
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