As docbert commented above, the uniquely strange behavior here might be due to the same flight number on both segments, plus then the normal married segment mischief. I realize this is not terribly rare on mainline UA, but what _does_ seem odd here is that this "same flight, two unrelated segments" number on this afternoon SJC-IAH-BWI flight has persisted for at least three years; I take it often. Normally the flight number, and the "same number oddity", turns over every few months, and thus the annoyance is limited. It's actually quite a pain -- the selection of seats to reserve is greatly restricted, for example, as the identical seat has to be open on both segments. And CPUs are similarly restricted to "both legs or no legs", like the Island Hopper.

It's gone on for so long on this one flight that I sometimes wonder if this is some weird pilot or FA pay issue, where the company is trying to thwart the union contract. Or possibly something competitive on a mail or freight contract; there are a lot of daily USPS charters out of SJC to the east coast.