Let's not forget that throughout the merger, one of US Airways' favorite things to point to in self-promotion has been *A membership, as a way of distinguishing itself from JetBlue, AirTran and Southwest. I would agree with the "this is standard legalese" perspective on this--and also note that though US may not be the most valuable *A member, the others have no reason to want it out, since US Airways still has a base of X thousand (I really don't know how many) loyalists on the East Coast who look toward UA, LH & co. when flying outside of the immediate area and who would otherwise have no particular preference. The costs of having US in the alliance (allowing DM members to redeem miles, lounge access, etc) are small compared to the extra traffic--the fact that the three alliances exist to begin with will testify to that.