A United Airlines Boeing 757 jet that was backing out of a gate at San Francisco International Airport crashed into a SkyWest plane carrying 60 passengers and crew Sunday night in what airport officials called a serious accident.
          The crash occurred at 7:30 p.m. at domestic Terminal 3 as the United plane was being taken out of service and moved without passengers from Gate 80 to a hangar for maintenance. The passengers onboard the SkyWest plane, which was headed to Boise, Idaho, were not injured, said Airport Duty Manager Lily Wang. They were quickly evacuated from the plane, a Canadian Regional Jet 700, by stairway and walked 100 to 150 yards to the terminal.
          The impact caused damage to both planes: Both had part of their tails sheared - specifically the vertical stabilizer assembly - and both had damage to their engines. "The 757's tail basically went on top of the regional jet," Wang said. "It is human error. It is dark out there, it is nighttime. It could be (United) not seeing that other airplane because it is very low." The crash will be investigated by the Federal Aviation Administration, and is certain to raise new questions about safety at the airport. In a report released in October by the FAA, SFO was declared one of the nation's riskiest airports in terms of near-collisions on runways or incidents in which pilots get confused while taxiing around the airfields.