Overview
A ground collision occurred at night in an airport alleyway between an outbound United Boeing 737, registered as N371UA, and an outbound American Boeing 767, registered as N335AA. The aircraft made tail-to-tail contact.
Sequence of Events
The United 737 was under tug control during pushback from gate number 77, without the assistance of wing walkers. The American 767 had previously been pushed back from gate number 63 with wing walkers and had begun taxiing from the same alleyway.
According to the tug driver of the United 737, during the pushback she observed a nearby food service truck and initially reduced speed to allow it to pass. She then resumed pushing the 737 toward the designated alleyway location. Suddenly, an impact occurred, at which point the tug driver saw an American 767 already in the alleyway.
Operational Responsibilities and Prior Awareness
United management stated that during pushback operations, the tug driver was responsible for ensuring adequate clearance. Nine months before the collision, United management was aware that aircraft using gate number 77 did not meet the minimum 25-foot wing tip clearance required by the City of San Francisco. City personnel had agreed to allow United to use the gate provided that United "guarantee the use of wing walkers."