I certainly don't know what ACA's true motivation is. Perhaps they are working with Richard Branson to become his vehicle for entry in to the US market, or maybe they just don't think that United has much of a future. What I can predict with some certainty is that United is not going to abandon Dulles if ACA jumps ship.
While United has never been a major player in the northeastern US, it has had one pocket of strength, and that's Washington, DC. This dates back to the 1961 acquisition of Capital Airlines which was based at National Airport. Dick Ferris tried to start a north/south hub at Dulles back in the early 1980's even before United had any transatlantic flights. Unfortunately, American was trying to build a hub at Raleigh/Durham, Piedmont was building up Baltimore and Charlotte, and Eastern was still in the picture. There was simply too much capacity being dumped in the market and both United and American pulled back.
Today, Dulles is really a hub once a day during the late afternoon and early evening when the transatlantic flights arrive and depart. While the ACA flights certainly add valuable feed to United's network, I strongly suspect that most domestic connections to and from the transatlantic flights are already carried on United mainline flights to a few key cities such as LAX, SFO, OAK, PDX, SEA, SAN, PHX, LAS, DEN, ORD, DFW, BDL, MCO, MIA, MSY, and TPA. If necessary, United could replace ACA service to larger cities such as BUF, ROC, DTW, CLE, IND, etc. with mainline service or another United Express carrier. I'd have a hard time believing that feed from Binghamton, NY, Greenville, SC, or Charleston, WV would make or break United's Dulles operation. In other words, it would not be necessary to replicate the entire ACA pattern of service to make Dulles work.
ACA's schedule of flight throughout the day under the United Express banner gives United a stronger presence in the local market that helps United compete for frequent business flyers and corporate travel accounts in the Washington area. Losing ACA would therefore not be good for United. However, now that USAirways is slated to join the Star Alliance and is already code sharing with United, ACA is not nearly as important to United as it once was. Even if USAirways does not directly feed passengers to the Dulles hub, the marketing combination of the top two carriers in the Washington area gives both carriers a strategic advantage over all others when competing for local traffic.
It's interesting to note that on this same topic on the USAirways board there is speculation that Dulles will be phased out and that Philadelphia will become the new Star Alliance gateway to Europe. I would be very surprised if this were to happen. Dulles is a natural gateway to Europe and the Middle East. The Washington/Baltimore metro area has one of the largest populations in the country and of course is the national seat of government. The metro area also has above average per-capita income and education levels leading to a higher proclivity for foreign travel. With government and tourism traffic a given, Dulles has a huge local market and competitive advantage over other gateway cities such as Philadelphia, Charlotte, or even Boston. I suspect Dulles could support a fair amount of tranatlantic flights with no domestic feed at all.
Given this, I would be very surprised to see United downsize or abandon its principal transatlantic gateway should ACA decide to partner with another airline or strike out on its own. If United were to do so, it would be squandering a key strategic asset, something which it cannot afford to do.
50 PM ual06 wrote: 
