NTSB Identification: SEA08LA061B
Scheduled 14 CFR Part 121: Air Carrier United Airlines Inc.
Accident occurred Sunday, January 13, 2008 in San Francisco, CA
Probable Cause Approval Date: 08/28/2008
Aircraft: BOEING 757-222, registration: N508UA
Injuries: 61 Uninjured.

NTSB investigators may not have traveled in support of this investigation and used data provided by various sources to prepare this aircraft accident report.

A Boeing 757-222 airplane and a Bombardier Inc. CL-600-2C10 were substantially damaged when the tails of both airplanes collided during the pushback process from two adjacent terminal gates during night visual meteorological conditions. The flight crew of the CL-600-2C10 reported that during the final stages of pushback from gate 79, they were in a stopped position with both engines running while their ground crew was in the process of disconnecting the tug when the collision occurred. Company maintenance personnel stated they were pushing the 757-222 back from gate 80 without the use of wing-walkers or tail walkers to relocate the airplane to another location on the airport and did not see the CL-600-2C10. Review of Air Traffic Control (ATC) communication recordings between ground control and both airplanes revealed that the 757-222 was initially cleared for pushback onto taxiway alpha from gate 80. About 41 seconds later, the ground controller cleared the CL-600-2C10 to push back onto taxiway alpha from gate 79. The recordings revealed that the ground controller did not advise either aircraft of near simultaneous adjacent pushback operations. The controller stated that he believed there was room for both aircraft to push back and did not foresee a traffic conflict.

The National Transportation Safety Board determines the probable cause(s) of this accident to be:

The company tug operator's failure to maintain clearance with another aircraft during the pushback process. Also causal was the ground controller's failure to alert the pilot of the other aircraft and tug operator of this airplane of the simultaneous pushback occurring from adjacent gates. Contributing to the accident was the company's pushback operation without the use of wing/tail walkers.

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