Safety experts said finding the cause of a plane crash in Montana that killed 14 is likely to be significantly complicated by the absence of black boxes, key radar data or any mayday call from the single-engine aircraft.

With no cockpit voice recorder or a flight data recorder, investigators say it could take months to pinpoint a cause. They are looking into whether an overloaded cabin or ice might have contributed to the accident.

Fourteen people died Sunday when the single-engine Pilatus PC-12 nose-dived into a cemetery near the Butte airport and then burst into flames, officials and witnesses said. An experienced pilot was behind the controls.

Seven adults and seven children from three California families were killed. 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.

Click to view photos from the crash.

While descending toward Butte's Bert Mooney Airport, the plane passed through a layer of air at about 1,500 feet (500 meters) 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 in New York State last month, killing 50.

A possible stall created by ice — and the pilot's reaction to it — have 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."

There will not be any radar data of the plane's final moments for investigators to examine — like thousands of small airports, the Butte airport does not have a radar facility. The radar at the Federal Aviation Administration's en route center in Salt Lake City, which handled the flight's last leg, does not extend as far as the Butte airport.

The last radio communication from the turboprop's pilot was with the Salt Lake City center when the plane was about 12 miles (19 kilometers) 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.

Mark Rosenker, acting chairman of the National Transportation Safety Board, 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."

The pilot was identified as Buddy Summerfield, 65, of Redlands, California. Summerfield was a former military flyer who had logged 2,000 hours flying the type of plane that crashed, according to federal officials.

Former chairman of the transportation safety board Jim Hall said there were similarities between the Montana crash and a 2005 crash near Bellefonte, Pennsylvania, in which a pilot and five passengers were killed. The plane in both cases was the Pilatus PC 12/45, and in both there were reports of conditions conducive to icing at lower elevations and witness reports that the plane appeared to dive into the ground.

Rosenker said overloading and equipment failure also were being examined. He said the plane had 10 seats, including the two in the cockpit.

"It will take us a while to understand," he said. "We have to get the weights of all the passengers, we have to get the weight of the fuel, all of the luggage."