On May 30, 2005, at 0847 mountain daylight time, a de Havilland DHC-8-202, N454YV, operated by Mesa Airlines, Inc., as United Express Flight 7080, rode onto the top of the Lektro ground support vehicle during push back from the gate at the Denver International Airport (DEN), Denver, Colorado. The airplane was not damaged, and the ground support vehicle was damaged under the airplane nose wheels. Visual meteorological conditions prevailed at the time of the incident. The scheduled domestic passenger flight was being conducted on an instrument flight rules flight plan under the provisions of Title 14 Code of Federal Regulations Part 121. The captain, first officer, flight attendant, and 37 passengers on board were not injured. The flight was originating at the time of the incident and was destined for Gunnison, Colorado. According to the Mesa Airlines captain and SkyWest supervisor written statements, the aircraft was parked at the gate awaiting push back by SkyWest Airlines ground personnel. Two ground personnel (one supervisor, one trainee) were operating the Lektro ground support vehicle. During initial push back, the trainee turned the aircraft in the wrong direction, at which time, the supervisor took over control of the vehicle. During the supervisor's attempt to turn the aircraft around, the nose wheels rolled out of the vehicle's wheel cradle and up onto the Lektro vehicle. The aircraft was stabilized by Mesa maintenance personnel, and the crew and passengers deplaned without further incident. A SkyWest employee reported that she overheard a Mesa crewmember report to dispatch that the ground personnel was making a sharp turn and the crewmember thought the airplane was going to be pushed back into another airplane. At that point, the nose wheel slipped out of the craddle onto the ground support vehicle. According to a SkyWest internal report, the Mesa captain indicated that he had a safety concern about hitting another aircraft during pushback. The report stated the push back operation should have come to a stop and communication should have been conducted between the flight crew and ground crew to resolve all concerns about safe maneuvers. Examination of the aircraft by Mesa maintenance personnel revealed no damage. Per the manufacturer's recommendation, the nose gear assembly was removed and replaced, and the aircraft was returned to service.