What happened
On the ramp at Mitchell International Airport (MKE) in Milwaukee, Wisconsin, two Midwest Airlines Boeing 717-200 aircraft were involved in a ground collision. The first aircraft, N904ME (Flight 157), was parked at gate D36, while the second aircraft, N923ME (Flight 406), was parked at the adjacent gate, D34.
After Flight 157 completed its pushback, it remained stopped facing east, positioned perpendicular to the gates. The crew of Flight 406 prepared for their own departure; however, the tug driver notified the captain that a full pushback was not possible due to the position of Flight 157 behind them. Seeking to maintain an on-time departure status, the captain of Flight 406 instructed the tug driver to proceed with as much movement as possible. The tug driver moved the aircraft approximately 5 to 6 feet before wing walkers signaled to stop.
The aircraft remained stationary for several minutes after the brakes were set. When the crew of Flight 157 began taxiing forward and initiated a left turn, the aircraft experienced a jolt. Upon inspection, it was determined that the aircraft had struck the stationary plane.
The investigation
The investigation examined the physical damage to both aircraft. N904ME sustained minor damage to the outboard corner of the right side elevator trim tab end cap. In contrast, N9<0xA0>923ME sustained substantial damage to the left side elevator and the left side elevator trim tab.
Findings
Following the incident, a red Pushback Clearance Reference Line was painted on the ramp area perpendicular to gates D30 through D38. Midwest Airlines subsequently issued a Ramp Training Procedural Communication requiring that both main landing gear remain on the alley side of this reference line during pushbacks. Furthermore, the airline revised its Company Operations manual to prohibit "partial push backs" performed solely for the purpose of recording an on-time departure, mandating that pushbacks only begin once the area behind and beside the aircraft is clear for a complete, uninterrupted maneuver.