DL has said it is not interested in a full merger or acquisition of AA based on the recognition that DL plus AA would be too large and overlap on too many key routes.
That said, a combined AA and US would have antitrust problems in WAS that would prevent a full merger from occurring w/o divestitures that are not much different in terms of relative size compared to DL and AA in NYC.
What alot of people consistently seem to miss is that AA represents the best and probably last opportunity for DL to address its strategic needs as well - a greater presence at LHR and in Latin America as well as filling out its domestic route system w/ a viable Texas hub.
At the same time, you can be absolutely certain that DL will act before it stands by and allows US to acquire AA and grow to be on par w/ DL on the east coast.
BA could indeed only acquire 25% of AA... but don't rule out the possibility that DL could decide that to ditch AF/KL to hook up w/ BA. AF/KL is in the midst of its own major transformation that will take years to complete and still might not deliver profit levels of the size that is necessary. Since a joint venture means that DL shares profits and losses w/ AF/KL/AZ, if its European partners are underperforming other European partners, then DL has reason to ally with those that maximize its profit. DL + BA/IB would be far better suited to providing a more balanced European network for an alliance than AA/US is.
Finally, don't rule out that if labor difficulties at AA escalate, DL could choose to find a partner - either in terms of another airline or an investment company - that would allow DL to split AA up, taking the parts of AA that DL needs and allowing the rest to be spun off into another company. AS and B6 might say there are not interested in merging with AA but they would most definitely be interested in further discussions if the opportunity to came along to take over a couple AA hubs.
What should not be underestimated is that unless UA decides to jump in the ring, DL has the deepest pockets of any of the potential acquirers - certainly deeper than US, has a very good track record of making mergers work and delivering value to its former creditors, and has the current stability and success necessary to demonstrate it can take on another new challenge.
And honestly a lot of AA people might find that working for DL provides the greatest opportunity for them to continue in their careers.
Many AA pilots are saying they won't work for less than DL pay rates. It shouldn't be lost that part of DL's reason for pushing through a pay raise for its pilots when it did was to put pressure on AA and its ability to restructure.
