Originally Posted by FlytheTail
In particular, I'm interested in bonus mileage %, domestic upgrades, and perhaps most importantly, comp. international upgrades.
DL/AA/UA give 100% mileage bonuses. All three issue systemwide upgrade certificates to top tiers valid for international travel. DL and AA offer complimentary domestic upgrades on virtually any fare, while UA offers complimentary domestic upgrades only on full fares. DL offers complimentary CRC membership. UA/AA are the only U.S. carriers that offer international first class with true lie-flat seats.