On September 12, 2014, about 2026 central daylight time, an ExpressJet ERJ145XR, dba United Express flight 4528, N16147, was struck by a United Airlines baggage tractor while taxiing to the gate at Chicago O'Hare International Airport (KORD), Chicago, Illinois. There were no injuries to the 37 passengers and crew members onboard the airplane and the airplane sustained substantial damage. The tractor driver received minor injuries. The flight was operating under 14 CFR Part 121 as a regularly scheduled passenger flight from Joe Foss Field (KSFD), Sioux Falls, South Dakota, to KORD. According to the operator, the flight had just landed and was taxiing on taxi-way A from the east and had just switched to United Ground Control. The flight was instructed to taxi from A to the alley and transition to the "B" side "J"-line and taxi to gate E2. As the airplane entered the United Airlines control area, a baggage tractor drove into the path of the taxiing airplane on the roadway between the gates C-29 and B-16. The airplane was unable to stop and the right wing struck the moving baggage tractor, knocking it onto its right side. The airplane sustained substantial damage to the right wing and right leading edge.