Video: Investigators search for clues to San Francisco plane crash While federal investigators began piecing together what led to the crash, San Mateo County Coroner Robert Foucrault disclosed that he was looking into the possibility that one of the two teenage passengers who died actually survived the crash but was run over by a rescue vehicle rushing to aid victims as the plane burst into flames. At a news conference, NTSB chief Deborah Hersman disclosed the Boeing 777 was traveling at speeds well below the target landing speed of 137 knots per hour, or 157 mph. Ms Hersman described the frantic final seconds of the flight as the pilots struggled to avoid crashing. Seven seconds before the crash, pilots recognised the need to increase speed, she said, basing her comments on an evaluation of the cockpit voice and flight data recorders that contain hundreds of different types of information on what happened to the plane. Three seconds later, the aircraft's stick shaker - a piece of safety equipment that warns pilots of an impending stall - went off. The normal response to a stall warning is to boost speed and Hersman said the throttles were fired and the engines appeared to respond normally. At 1.5 seconds before impact, there was a call from the crew to abort the landing. The details confirmed what survivors and other witnesses said they saw: an aircraft that seemed to be flying too slowly just before its tail apparently clipped a seawall at the end of the runway and the nose slammed down.