Air accident investigators say the pilot of a crashed Asiana plane in San Francisco initially told flight attendants not to evacuate the plane.
The crash of the Boeing 777 on Sunday killed two teenage girls from China and injured more than 180 people.
US Transportation Safety Board head Deborah Hersman said passengers were told to stay in their seats after the crash landing.
The evacuation began 90 seconds later, when a flight attendant saw fire outside the window.
First emergency crews arrived 30 seconds later.
The pilot at the controls was still training on Boeing 777 jets and his supervisor was making his first flight as a trainer.
The BBC reports Deborah Hersman said the pilot who landed the plane later told investigators he was blinded by a light at about 500ft (150 metres) - which would have been about 34 seconds before impact and the point when the Boeing began to slow down.
The possibility that the flash was caused by a laser was not being ruled out, Ms Hersman added.
Aside from the pilot's relative inexperience in a Boeing 777, it has also emerged that the instructor pilot reported noticing seconds before the crash that the auto-throttle was not maintaining the correct airspeed.
US investigators are continuing to review flight data and video footage, and have interviewed all four pilots and half of the flight attendants. The additional attendants remain in hospital, among them three who were ejected from the rear of the aircraft when the tail ripped off on impact.