UA has had PIT/LAX for years, and AA recently started a flight, too! I'm wondering if AA started with the anticipation of the UA flight going away when US switches to OW from :-:A.

That said, I think right now, with 2 nonstops a day, a DL flight would be over the top, but, I'm not even sure it would be feasible if it was the ONLY flight each day. The PIT airport employees I've talked to seem to think a PIT/SEA nonstop is possibly in the works.