On a RT itinerary I was looking at earlier today (two legs on AC metal, two legs on UA metal), UA.com did not want to show me the itinerary I wanted unless I listed each leg separately using multi-city, and even then listed it for $1900 with two legs in first, while Orbitz listed it for $1100. (AC's website would not even show one of the UA legs.) I find that pretty annoying, but also a lesson to always check ITA and Orbitz or Kayak.