Investigators scrutinized the pilot's actions in the final moments of Flight 3407 and tried to determine whether anything on the airplane broke mid-flight, while families of the victims placed roses at the crash site Monday.
After a seemingly routine flight, the airplane endured a 26-second plunge before smashing into a house in icy weather about six miles from Buffalo Niagara International Airport on Thursday night, killing 49 people on the plane and one on the ground.
Though ice has emerged as a possible factor, the cause has remained elusive in part because there was no distress call from the pilot, no mechanical failure has been identified and the plane was so severely damaged.
Shortly before the crash, the crew notified air traffic controllers that there was significant ice buildup on the windshield and wings even though they had turned on the plane's deicing system 11 minutes after leaving Newark, N.J.
National Transportation Safety Board member Steve Chealander drew attention to the crew's actions when he said Sunday that the pilot appeared to ignore recommendations by the NTSB and his employer that the autopilot be turned off in icy conditions. The autopilot remained on until an automatic system warned that a stall could occur, pushed the pilot's yoke forward and shut the autopilot off.
Chealander acknowledged that it was possible that the pilot overreacted by yanking the yoke back, further destabilizing the plane, but he said that was one of an almost unlimited number of possibilities.
Kirk Koenig, president of Expert Aviation Consulting of Indianapolis and a commercial aviation pilot for 25 years, said the airplane may have been in a predicament that would challenge even the most experienced pilots.
For example, if ice were forming on the wings, the pilot would want to put the nose of the plane down and increase power; if the icing were on the tail, the opposite would have been required, pulling the nose up and reducing power.
"Things happened so quickly and they were so low to the ground that it would not have mattered if Chuck Yeager and Neil Armstrong were flying the plane; there wouldn't have been a different outcome," Koenig said.
The plane's deicing system was apparently working, the NTSB has said. That system includes strips of rubber-like material on the wings and tail that expand to break up ice, then contract and expand again to break up new ice.
Aviation safety consultant Eric Doten said it is possible to turn on the system too early. Ice can form over the inflated bladders; when the bladder contracts and inflates again, it cannot inflate far enough to break up the ice, he said.
Also Monday, relatives of the victims made their first trip to the scene. They left red roses dangling from temporary fencing and in a semi-circle on the ground.
The plane landed diagonally, with the tail toward the back of the house and the nose facing the street, allowing it to miss the homes on either side. The destroyed home's four front steps remain standing, but lead nowhere.
More than 2,000 people, including relatives of the victims, turned out for a community prayer service Monday.
"We feel it's a miracle that more houses weren't destroyed and more people killed," said Ora Ganschow, 79, who lives four blocks from the site.
Wearing blue dress uniforms, members of the Clarence Center Volunteer Fire Co. carried single long-stemmed roses -- one for each victim -- to the altar, placing them into a crystal vase as a soloist sang "Amazing Grace."
Authorities said gawkers continue to be a problem, forcing officials to again close a road that leads to the suburban Clarence neighborhood. Three people have been arrested, including a man caught hiding behind a home and videotaping the crash site Friday.
Much of the plane has already been removed. A crane was brought in to move the engines so investigators could determine whether the engines and their blades were intact when they hit the ground.
Investigators also were looking into the flight crew's actions.
The captain, Marvin Renslow, 47, was believed to be handling the duties of the pilot during the final moments aboard the Dash 8 Q400 plane, operated by Colgan Air. He had 3,379 hours of flying experience but had only flown the Dash 8 since December.
The flight's first officer, Rebecca Lynne Shaw, 24, had 2,244 hours of experience and had flown the Dash 8 for 774 hours.
Chealander said investigators would research Renslow's and Shaw's histories, would analyze the plane's maintenance records and were asking pilots who were in the air around Buffalo on Thursday whether they had to deal with ice.
Associated Press writers Joan Lowy, William Kates, Carolyn Thompson and John Curran contributed to this report.