Clearly they make these decisions based on expected profits (or more precisely, net present value calculations).

When the entire economy of Asia isn't in a tailspin, NRT is a gold mine. Major controls on who can fly there and how often. Demand exceeds supply and so planes go out full and at above-market fares.

FRA on the other hand isn't such a gold mine, and it hardly fit into Delta's route structure.

Pan Am's structure, on the other hand, was a bit of a dinosaur. First, their decision-making about which routes to serve was often political or ill-considered. Second, it was outdated in a post-deregulation world. Once they had real competition many of their earlier decisions were no longer profitable.



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"Would you convey my compliments to the purist who reads your proofs and tell him or her that I write in a sort of broken-down patois which is something like the way a Swiss waiter talks, and that when I split an
infinitive, d*** it, I split it so that it will stay split."
- Raymond Chandler, to the editor of the Atlantic Monthly, 1947

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