201307111100Asiana Airlines Boeing 777 pilot crashed in San Francisco
Deborah Hersman, head of the National Transportation Safety Board (NTSB), otter case said cabin crew had sought guidance from the cockpit after Saturday's crash, which left two people dead and more than 180 injured.
Pilots initially told flight attendants not to begin evacuation procedures, Hersman said on Wednesday.
It was only after cabin staff alerted the cockpit to flames spreading outside the plane that the order was given to begin evacuation.
"We don't know what the pilots were thinking, though I can tell you in previous accidents there have been crews that don't evacuate, they wait for other vehicles to come to be able to get the passengers out safely," Hersman said.
Hersman suggested that pilots in the cockpit may not have been in a position to spot the fire outside the plane.
She emphasised that once flames were sighted, the evacuation began swiftly - about 90 seconds after impact.
"Certainly, if there is an awareness that there's fire on board on aircraft, that is a very serious issue ..." Hersman said.
"The pilots are in the front of the aeroplane, they really don't have a good sense of what's going on behind them fr4 pcb, they need to get that information from the flight attendants, but we will certainly be looking into that issue.
"Hindsight is 20-20. We all have a perspective that's different than some of the people who are involved in this.
"We need to understand what they were thinking, what information they had, what their procedures are, if they complied with those procedures and if that evacuation took place in a timely manner."
Emergency response vehicles arrived on the scene about two minutes after the crash and began extinguishing flames three minutes after impact.
Hersman said interviews with the plane's crew had given investigators a vivid portrait of the scene on board the stricken aircraft moments after the crash.
Two emergency slides had inflated inwards inside the cabin, pinning two attendants who needed to be cut free as the evacuation began.
It was not immediately known why the slides had deployed inside the aircraft.
Flight 214 crashed when it clipped a seawall short of the runway, skidding out of control, label sticker shredding the tail of the plane and catching fire.
The NTSB has already determined that the plane was travelling well below the target speed necessary for landing.
It has also emerged that the otherwise experienced pilot of the plane, 46-year-old Lee Kang-Kuk, was undergoing his first major training on the Boeing 777.