All 14 people on board were killed, half of them small children.
While descending Sunday in preparation for landing at the Bert Mooney Airport in Butte, Montana, the turboprop plane passed through a layer of air at about 1,500 feet that was conducive to icing because the temperatures were below freezing and the air "had 100 percent relative humidity or was saturated," according to AccuWeather.com, a forecasting service in State College, Pennsylvania.
Safety experts said similar icing condition existed when a Continental Airlines twin-engine turboprop crashed into a home near Buffalo Niagara International Airport last month, killing 50.
A possible aerodynamic stall in which ice causes the plane to lose lift, and the pilot's reaction to it, has been the focus of the Buffalo investigation.
"It's Buffalo all over again, or it could be," said John Goglia, a former member of the National Transportation Safety Board. "Icing, given those conditions, is certainly going to be high on the list of things to look at for the investigators."
Mark Rosenker, acting NTSB chairman, told reporters in Montana that investigators would look at icing on the wings as a factor.
"We will be looking at everything as it relates to the weather," he said.
The single-engine plane, designed to carry 10 people, crashed 500 feet short of the Montana airport runway Sunday, nose-diving into a cemetery and killing seven adults and seven children aboard. Relatives said the victims were headed to an exclusive resort on a ski vacation, and gave the children's ages as 1, 3, 5, 7 and 9, plus two 4-year-olds.
According to CBS News Correspondent Hattie Kauffman, witnesses said it looked like the pilot was struggling to maintain control.
"I thought it was a stunt plane because it was going into high-G turns and such," 14-year-old eyewitness Kenny Gulick told CBS' The Early Show Monday. "All of the sudden it went into a nosedive."
CBS News correspondent Nancy Cordes reports the plane's airworthiness certificate was current, according to FAA officials.
Safety experts said finding the cause of the crash is likely to be significantly complicated by the absence of either a cockpit voice recorder or a flight data recorder; neither is required for smaller aircraft that don't fly commercial passengers.
Hours after the crash, federal investigators had focused on overloading as a possible cause.
"It will take us a while to understand," Rosenker said. "We have to get the weights of all the passengers, we have to get the weight of the fuel, all of the luggage."
Goglia said the Pilatus has a powerful engine for its size and is unlikely to be affected by the additional weight of a few children "unless they had an awful lot of baggage."
One key in the Butte crash will be whether the pilot had changed the position of the aircraft's wing flaps for landing because changing the configuration of the wings by moving the flaps is where icing problems often show up, said Peter Goelz, a former NTSB managing director.
The last radio communication from the turboprop's pilot was with the Salt Lake City center when the plane was about 12 miles from Butte, said Doug Church, a spokesman for the National Air Traffic Controllers Association. The pilot told controllers he intended to land at Butte using visual landing procedures rather than relying on instruments, which is not unusual, Church said.
Rosenker confirmed that the pilot said nothing to controllers to indicate he was having trouble, including during radio conversations earlier in the flight when the pilot notified controllers he intended to divert from the flight's original destination of Bozeman, Montana, to Butte.
"We don't know the reason for the requested change to the flight plan," Church said. "We don't know whether weather was a factor in Bozeman. There was no apparent reason given for the change in flight plan from Bozeman to Butte."
Lewis Pullen, father of one of the crash victims, told CBS, "People who planned this vacation did a wonderful thing, and it turned out to be a tragedy."