You're up in the mountains, right? Whereabouts? I'm in Athens, and though I briefly considered flying my two on a domestic flight to NYC or DC or Chicago and using another airline, ultimately I decided that for sanity's sake - both the kittens' and my own! - we'd be best off flying from Atlanta. It's going to be a long enough trip - two hours to Atlanta, then cargo check-in four hours before the flight, then an eight-hour flight, then up to 4-5 hours to clear once we land at Gatwick, then a 5-6 hour drive up to Middlesbrough - that I really didn't want to add any more stress to the whole ordeal, even if I did get a quote for $1600 when I spoke to the guy at BA world cargo! Unfortunately for us, the only approved route out of Atlanta is with BA, and they seem to be the most expensive by far - but when you take into account the cost of another leg - my ticket, the cats' tickets, and the excess baggage fees - it really doesn't add up to be any cheaper.
I'm a bit miffed about the fact that flying two cats costs double what one would cost, especially since it's just as easy to do most of the paperwork/handling/etc. for two from one owner as one, but whatever....