Will the revenue premium offset the CASM increase? I willing to bet that it does. However, will UA be able to keep enough seats free to sell to the high-yield O/D passengers in these markets? I'm talking about the UA flyers who decide to route (for example) SEA-SFO-JFK instead of SEA-ORD/DEN-NYC for a chance to upgrade into business class and a guarantee of E+ across the country. It would be a mess for UA to re-write their flight applications and routings on all their fares (though it could be done). Cause I promise that the smart flyer will take their cheap fare and route via these flights if they can from places like SEA, PDX, SAN, PHX, etc.
Another issue with this service looks to be aircraft utilization. 13 planes for 24 flights a day? So each one flies 2 flights a day with one spare? Seems pretty low to me. UA should figure out how to work in a couple extra tags to DEN or SEA. With the 3-classes of international flights being sold from LAX/SFO to Australia and Asia, having a 3 class plane to connect from/to those flights to SEA/DEN (which I imagine provide a good amount of feed to those int'l flights) would be a nice benefit to the F/C passengers. Instead of sitting in domestic F on their first/last leg, at least they get another leg of int'l F/C. Would the extra cost of operating a couple extra shorter flights a day outweigh the potential benefit?
Anyway, I think this is a good idea, and hopefully it is successful. Perhaps LAX/SFO to IAD on a couple of flights would be the next step if it works?