United Airlines is limited to 255 76/70 seat aircraft (E175/E170/CRJ900) in the Express Fleet. Thise aircraft types are currently assigned to SkyWest, Republic, and Mesa. CommutAir will probably not see any 175/170 in the operation from United unless one of those 3 airliens can fullfill thier operations. However expect SkyWest or Repubic to pick up any 175/170 Mesa cant fly.