By Alan Levin, USA TODAY

WASHINGTON — As the turboprop droned toward Buffalo in darkness, the pilots did the inexplicable.

TRANSCRIPT: Pilots joked around before crash

NTSB: Buffalo crash animation

The turboprop had gotten too slow for safe flight and a warning system known as a "stick shaker" began vigorously vibrating the control column. Pilots are trained to react to such warnings by speeding up and lowering a plane's nose.

But Capt. Marvin Renslow did the opposite, according to a dramatic video animation and thousands of pages of documents released Tuesday by federal crash investigators. Renslow yanked the nose up and slowed the plane even more.

The actions by Renslow, 47, and co-pilot Rebecca Shaw, 24, are baffling, according to veteran accident investigators and a senior manager at their airline, Colgan Air.

"It's just opposite of what any pilot would do," said Michael Barr, an aviation safety instructor at the University of Southern California's Aviation Safety and Security Program.

"I did not see that the crew performed … correctly," said John Erwin Barrett, Colgan's director of flight standards, who testified in the first day of a three-day hearing into safety issues raised by the New York crash.

The crash Feb. 12 near Buffalo killed all 49 people aboard the Bombardier Q400 and one man on the ground. The flight from Newark to Buffalo was being operated by Colgan under contract with Continental Connection.

The reasons for Renslow's and Shaw's actions may never be known for sure, but the National Transportation Safety Board (NTSB) data at least begin to shed light on what might have led to their actions. The documents highlight numerous safety issues being examined by investigators.

According to NTSB documents:

• Both pilots may not have gotten adequate rest before the flight. Shaw had taken an overnight flight from Seattle before reporting to work and told Renslow she was feeling sick. Renslow logged into an airline computer system at 3 a.m. on the morning of the crash.

• Renslow had failed four Federal Aviation Administration check flights to determine whether he was qualified to fly. He also failed an airline check. He was able to pass each of the checks after retaking the tests and the airline issued a statement saying his skills were adequate.

• Investigators found that most pilots at Colgan had not been trained how to use a second safety device that attempted to save their plane as they went out of control. Known as a "stick pusher," it automatically pushes a plane's nose down to pick up speed when the aircraft gets dangerously slow. When it activated, Renslow overrode it, keeping the nose pointed skyward.

• In the minutes before the crash, the pilots engaged in several minutes of conversation that was not relevant to the flight, according to a transcript of their conversation. Such discussions are forbidden while flights are below 10,000 feet under federal law.

• The airline showed its pilots a video of an unusual type of icing that prompts planes to nose-dive into the ground even though the Q400 is not susceptible to the problem. That could help explain why Renslow pulled the plane's nose upward, even though investigators have found no evidence that icing played a role in the accident.

The union for the pilots, the Air Line Pilots Association, said it would be wrong to simply blame the pilots without looking at broader issues of training.

For example, pilots are trained repeatedly on how to react when their plane gets too slow, as occurred in the Buffalo crash. But the training does not accurately reflect the real-world distractions that occur in actual flight, said Capt. Paul Rice, the union's vice president.

"It's not realistic," Rice said.

Colgan spokesman Joe Williams defended the airline's training, saying it had been approved by federal aviation regulators.

Even though the NTSB records offer clues about why the accident occurred, it will take many months of analysis and additional investigation to determine the cause of the crash, Barr said.

"Is it training? Is it stress?" he said. "It could be almost anything."