Just my opinion on airlines I have flown long haul on;
Virgin Airways; great service, food, staff, and free stuff on the plane like socks, toothbrush. (leg room in economy not great)
Delta: one of the best American Airlines
BA: good food, leg room ok, standard service
Thompson; probably the best leg room I have found economy long haul. Not bad food and service too.
Never flown American Airways.
KLM; (Dutch so doubt they fly from UK) reasonable leg room (try to get economy plus) excellent service. A constant snack and drink bar you can help yourself to!
Have fun in Atlanta!
