Well, considering UA's long standing relationship to PW (all the way back to Boeing Air Group) they often opt for Prat interests in engines, even when they are not the best choice. All of their 744s, 767s, 757s, and 777s. The A320 family planes are all IAE, which has been identified as a Prat concern. The only planes that are not Prat are the 737s, which are exclusively CFM