BUFFALO -- The commuter plane that crashed near Buffalo was on autopilot when it went down in icy weather, indicating that the pilot may have violated federal safety recommendations and the airline's own policy for flying in such conditions, a federal official said Sunday.

Steve Chealander, a National Transportation Safety Board member, said the company that operated the flight recommends pilots fly manually in icy conditions. Pilots are required to do so in severe ice.

"You may be able in a manual mode to sense something sooner than the autopilot can sense it," Chealander told The Associated Press in an interview, explaining why the NTSB also recommends that pilots disengage the autopilot in icy conditions.

The preliminary investigation indicates the autopilot was still on when the plane crashed, he said. That has not been confirmed by information from the plane's flight data recorder.

The pilots of Continental Flight 3407 discussed "significant" ice buildup on their wings and windshield just before crashing Thursday night in a suburban neighborhood near the Buffalo airport. Fifty people were killed.

The flight was run by Colgan Air, which operates a fleet of 51 regional turboprops for Continental Connection, United Express and US Airways Express.

In a December safety alert issued by the NTSB, the agency said pilots in icy conditions should turn off or limit the use of the autopilot to better "feel" changes in the handling qualities of the airplane.

Chealander also said Colgan, like most airline companies, had begun following NTSB recommendations that pilots use deicing systems as soon as they enter conditions that might lead to icing.

He said it was not yet clear exactly when the pilot on Flight 3407 turned on the plane's advanced deicing system.