WASHINGTON — The crew of Continental Connection Flight 3407 violated federal regulations banning extraneous conversation or activities on approach to landing, prompting the airline that managed the doomed flight to later warn pilots against idle chatter and other inappropriate actions in the cockpit.

Sources with knowledge of the National Transportation Safety Board investigation said the probe will show that the pilot, Capt. Marvin D. Renslow, and co-pilot, Rebecca Lynn Shaw, violated federal rules that require a "sterile cockpit" when a plane is flying below 10,000 feet. Renslow piloted the plane that crashed in Clarence on Feb. 12, killing 50.

And about two weeks after the crash, Colgan Air — the Continental subcontractor that ran the doomed flight — sent its air crews a memo warning them against extraneous conversation and other inappropriate activities such as eating when flying below 10,000 feet, sources told The Buffalo News.

The revelation of the inappropriate conversation or activities of the Flight 3407 crew, which is expected to be detailed when the safety board begins three days of hearings on the crash on Tuesday, is part of an increasing focus on Renslow as the investigation continues.

Renslow, 47, failed three Federal Aviation Administration proficiency checks before joining Colgan in 2005, sources confirmed this morning.

While pilots often fail those tests once or twice, "it is fairly uncommon to fail three," said a source with knowledge of the safety board investigation of the crash. "That's a little high. But then, why did they hire him?"

Colgan's spokesman told The Wall Street Journal, which first reported that Renslow failed those tests, that the company believes Renslow, a former small business owner who changed careers to become a pilot, did not disclose those failed tests when he applied for a job.

Renslow also failed in his first attempt to qualify as a co-pilot on the Beech 1900 aircraft, and also had to try twice on tests to upgrade to captain on the Saab 340 turboprop.

After Flight 3407's stall warning system activated, Renslow pulled down on the plane's yoke — which is just the opposite of what he should have done, several aviation sources have said.

The NTSB hearings are expected to focus on why Renslow did that. And sources close to the investigation said the hearings are likely to point fingers not just at Renslow's abilities as a pilot, but also Colgan's training program.

The plane that crashed, the Bombardier Dash 8 Q400, includes an unusual feature that increases the speed at which the plane's stall warning system will activate when flying in icing conditions.

Colgan never provided pilots with any instruction in that unusual feature until the autumn before the crash, sources said.

In addition, Colgan's training program does not include simulator training into how pilots should react when the stall warning system activates, sources said.

Fatigue also may have played a role in the crash.

Sources told The Buffalo News that Renslow had been working an overnight shift only weeks before switching to the evening schedule that he was on the night the plane crashed.

As for the co-pilot, Shaw, the Feb. 12 flight came the evening after she had flown a red-eye flight to Newark from her home in Seattle, sources told The Buffalo News. Shaw had been with Colgan a little over a year.

The top two training officials at Colgan Air resigned in recent weeks.

Those officials, Darrell Mitchell and Ed Yarid, left the airline voluntarily, and their departures were unrelated to the crash, said Joe Williams, a spokesman for Colgan's parent, Pinnacle Airlines.

Mitchell is scheduled to testify at the safety board hearings.