It might depend if the two bidders contact each other behind the scenes and come to an agreement. As it is an auction, based on who is prepared to spend the most, one cannot really say who out of the two is most likely. One would think that TheAA would want it more but American Airlines do take a serious interest in their "AA" mark and fly a lot of long haul routes between the US and the UK. If Andrews & Arnold get it, i'll eat my laptop.
And I'll go 1 better and eat my desktop
American airlines probably got more money and cloat but it is .co.uk so let's see ?
Maybe alcoholics annomynous can put in a secret bid ?