I wonder why both UAL and AA are ordering both the 787 and A350? Aren't they just the same thing only different? i.e. don't they both do the same mission? Seems they would save a lot of maintenance training, pilot training, parts supply chain, etc. if they picked one or the other.

"American has inherited 22 A350 orders from US Airways, which operates the world's largest Airbus fleet. American will become the U.S. launch customer for the A350-900, with deliveries starting in 2017. Also, American has firm orders for 42 Dreamliners, with options for 58 more. The firm orders include both 787-800s and 787-900s. "