However, National Transportation Safety Board Chairwoman Deborah Hersman told reporters it will take months to complete the investigation into Saturday's crash landing, in which two people were killed and 182 were injured.
"This is just the tip of the iceberg," Hersman said. "There's a lot more that we have to review before we get to the end of this process."
The Boeing 777 crash landed when its landing gear and tail struck a seawall at San Francisco International Airport.
The jet was still on field near the runway Thursday, but the airport has been given control over the runway so crews can clear it and prepare it for use, the Los Angeles Times reported.
The pilot of Flight 214 has told investigators he was temporarily blinded just before the plane crashed.
Hersman said at a news conference Wednesday something flashed in the pilot's eyes as the Boeing 777 approached the runway at about 500 feet in altitude, the San Francisco Chronicle reported.
"We don't really know at this point what it could have been," she said.
The flash occurred 34 seconds before impact, about the same time the cockpit crew realized the plane was too low and not lined up properly to the runway.
Hersman said investigators want to know whether automatic controls in the cockpit were working, CNN reported.
The pilots were making a number of adjustments to the plane's instruments, including "multiple" automatic functions, in the last 2 1/2 minutes of the plane's flight, she said.
Pilots said the "auto throttle" was turned on but failed to regulate the plane's speed as expected.
"We need to understand what those modes were," Hersman said. "If they were commanded by the pilots, if they were activated inadvertently, and if the pilots knew what they were doing."
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