Investigators began gathering pieces of the incinerated wreckage of a commuter airliner early Saturday in search of clues to the cause of the fiery crash that killed 50 people.
Investigators have been examining instrument data and have listened to the last words of the pilot and co-pilot of Flight 3407 in an effort to determine if ice on the plane's wings caused the crash.
Meanwhile, workers have begun the somber task of removing the remains of the victims from the crash site.
Recovering the remains could take several days, said National Transportation Safety Board member Steve Chealander. "We're very sensitive to the families," he said.
The deadly accident comes just four months after the NTSB renewed its call for the Federal Aviation Authority to revise its regulations concerning deicing turboprop airplanes, accusing the FAA of complacency.
Officials say the crew of the Continental Connection flight remarked upon significant ice buildup on the wings and windshield shortly before the aircraft pitched violently and slammed into a house Thursday night.
Ice on the wings can interfere catastrophically with an aircraft's handling and has been blamed for a number of major air disasters over the years, but officials said they had drawn no conclusions as to the cause of this crash.
Chealander told CBS Early Show anchor Chris Wragge that while the flight recorders reveal the pilot had discussed "significant" accumulation of ice on the leading edge of the wings and the windshield, "That's not the only focus of the investigation. Yes, icing is a focus, but there are a number of other things.
"The phased approach of this investigation will see us through many channels over the next several months as we look at all aspects of the flight."
Chealander said the cockpit voice recorder is at the NTSB laboratory in Washington, D.C.
"Our technicians are continuing to audition that cockpit voice recorder, but they haven't indicated anything to me yet that there was any mayday call or distress by the crew," he told Wragge.
The landing gear was lowered one minute before the end of the flight at an altitude of more than 2,000 feet, and 20 seconds later the wing flaps were set to slow the plane down, after which the aircraft went through "severe pitch and roll," Chealander said.
The crew raised the landing gear at the last moment, just before the recording ran out. No mayday call came from the pilot.
The plane's system of deicing boots (pneumatic instruments on wings to remove ice) and heated propellors was switched on, Chealander said, but that the investigation will look into whether the system was working properly.
Ice buildup is one of a pilot's worst enemies.
Chealander said the NTSB has been pressing for more regulations to improve deicing.
"We don't like the progress that's taken place right now," Chealander said. "It's something that requires constant focus."
He said the NTSB had made recommendations "for several years."
A similar turboprop jet crash 15 years ago in Indiana was caused by ice, and after that the NTSB recommended more aggressively using pneumatic de-icing boots.
Last October, the NTSB renewed its criticism of the FAA over what it termed the agency's "unacceptably slow" pace in revising its recommended deicing procedures. In a blistering release it accused the FAA of complacency:
"The FAA has stated that no unsafe conditions exist that warrant actions beyond those that have already been completed or are in the process of being completed. The Board is concerned that the FAA has reached this conclusion based on a lack of accidents or serious incidents. During the 1990s, a number of accidents occurred involving airplanes that had passed the certification standards and for which the FAA believed there was no unsafe condition requiring action. Before another accident or serious incident occurs, the FAA should evaluate all existing turbo propeller-driven airplanes in service using the new information available, such as critical ice shapes and stall warning margins in icing conditions."In general, smaller planes like the Dash 8, which uses a system of pneumatic de-icing boots, are more susceptible to ice buildup than larger commuter planes that use a heating system to warm the wings. The boots, a rubber membrane stretched over the surface, are filled with compressed air to crack any ice that builds up.
The aircraft, bound to Buffalo from Newark, N.J., went down in light snow and mist - ideal icing conditions - about six miles short of the airport, plunging nose-first through the roof of a house in the suburb of Clarence.
All 44 passengers, four crew members, an off-duty pilot and one person on the ground were killed. Two others escaped from the home, which was engulfed in a fireball that burned for hours, making it too hot to begin removing the bodies until around nightfall Friday.
William Voss, a former official of the Federal Aviation Administration and current president of the Flight Safety Foundation, a nonprofit advocacy group, said the plane's near-vertical drop suggests that ice or a mechanical failure, such as wing flaps deploying asymmetrically or the two engines putting out unequal thrust, was the cause.
After the crash, at least two pilots were heard on air traffic control circuits saying they had been picking up ice on their wings.
The 74-seat Q400 Bombardier aircraft, in the Dash 8 family of planes, was operated by Colgan Air, based in Manassas, Va. Colgan's parent company, Pinnacle Airlines of Memphis, Tenn., said.
The pilot, Capt. Marvin Renslow, had been with the airline for nearly 3½ years and had more than 3,000 hours of flying experience with Colgan, which is nearly the maximum a pilot can fly over that period of time under government regulations.
It was the first fatal crash of a commercial airliner in the United States since Aug. 27, 2006, when 49 people were killed when a Comair airliner mistakenly took off from a Lexington, Ky., runway that was too short.