Concerns stemming from recorded 9-1-1 dispatch calls released Wednesday have focused on the sufficiency of medical response to the crash scene. Robinson explained that, as the emergency incident commander, his job was to set the distance for emergency vehicles that would arrive soon after him. "I parked far away from the plane, because as I positioned my unit, all other units fall in behind me," Robinson said. "No less than 30 vehicles, ambulances, fire engines, mobile units, commands, helicopters, are all parking from my point, behind me. I have to choose a safe point where everyone else is going to park."

As he took command of the scene, Robinson said his emergency units, including two rescue units, were already there and asking for more assistance for survivors. "They were there probably in a little over a minute," Robinson said of Station 2, dubbed "crash house" because of its proximity to the runways. "They got there fast. They were there before I got there, and I got there fast."

He went to work calling for a "recipe of resources," including mutual aid backup from San Mateo County and San Francisco, shuttle buses for survivor transport from the plane area to a safe distance, and the coroner's office -- just in case. By the time the first sweep for passengers was complete and firefighter had turned to fighting the fire, the "cavalry arrived" with backup assistance and a San Francisco Fire Department assistant chief, who took over command from Robinson, he said.

The call to evacuate the plane was made 90 seconds after it came to a halt on the runway, Hersman said on Wednesday. The crew first told passengers to remain seated, but an evacuation began after a flight attendant reported seeing fire outside the plane. The NTSB will examine whether proper evacuation procedures were followed, Hersman said, adding that "hindsight is 20/20."

Some passengers on the taped 911 calls reported not seeing ambulances and fire trucks. But emergency responders say procedures call for not bringing vehicles too close to the scene, in order to avoid chaos and collisions. In this case, there was also a worry that the plane could explode, said Mindy Talmadge, a spokesman for the San Francisco Fire Department.

"There's active fire, and there's fuel leaking, and there's debris all over the field, the last thing you want to do is take a chance of the plane exploding," she said in a phone interview on Thursday. A fire burned through much of the plane's cabin, although Hersman said the fuel tanks did not rupture.

Dudgeon said procedures called for a methodical approach in identifying the injured, starting in one spot and working forward. That could potentially leave some victims unattended for many minutes. "If you start to worry about go here, go there, you miss things," Dudgeon said. "As a paramedic, when you're doing triage, you start where you are. You keep moving forward until you've triaged everybody."