The copilot of American Airlines Flight 1420 told investigators today that despite towering thunderstorms Tuesday night, the clouds had created a "bowling alley effect" and that he could see down the "lane" all the way to the runway.

From a hospital bed where he is recovering from a broken leg, First Officer Michael Origel told investigators that the descent into the airport was normal and that he never lost sight of the runway.

But upon landing, things began to go wrong.

"The first officer said it was his perception that the plane hydroplaned down the runway and that he didn't feel the typical deceleration forces you would normally feel with thrust reversers and brakes," said George Black, a National Transportation Safety Board member.

The MD-80, carrying 143 people, apparently landed just as an intense thunderstorm moved over the airport. Evidence shows that the airplane slid down the runway for more than 5,000 feet before it went over an embankment and broke apart against metal instrument-landing-system poles. Nine people, including pilot Richard W. Buschmann, were killed and 83 people were injured.

Sources close to the investigation said that Origel's two-hour interview raises questions about whether the pilots may have neglected to pull the handle that would have turned on the spoilers -- movable panels on top of the wings that pop up when a plane touches down to help slow it.

Spoilers are a critical part of the airplane's braking system because they force the airplane's weight to settle on the main landing gear. The airplane's flight data recorder shows that the spoilers did not deploy immediately after landing.

"He [Origel] said he believed the captain did arm the spoilers" during the pre-landing checklist, Black said.

American Airlines' flight manual places responsibility for arming the spoilers on the nonflying pilot, which would have been Origel. But company officials said it is not unusual for the captain to turn on the devices because the handle is closer to the captain's seat.

Investigators said they cannot rule out the possibility that the automatic system malfunctioned. Without it, they said, the crew faced the daunting task of stopping the airplane on a rain-slickened runway.

"Without the spoilers to damp the lift, that airplane would be nothing but a very large skate with wings," said a veteran American Airlines pilot, who spoke on condition of anonymity.

Origel told investigators that upon landing, the crew lost sight of the end of the runway through the rain.

"He saw the captain go into heavy reverse," Black said. "At one point, the captain came out of reverse, and as the plane was going off the end of the runway, he remembered the captain going back into reverse."

Investigators and pilots said it is possible that Buschmann took the unusual step of turning the engine thrust reversers off and back on again in an attempt to keep the airplane from being blown off the side of the runway by a strong crosswind.

The thrust reversers, at the back of each engine, help slow an airplane. But they also decrease the effectiveness of the rudder, which controls the direction of the plane's nose.

Investigators said they are looking "equally" at other potential factors in the accident, including the bad weather and the pilot's decision to land in Little Rock when told of an approaching thunderstorm and heavy wind gusts on the field.

One safety board investigator said that weather experts are analyzing information from a Doppler radar site six miles to the northwest in hopes of being able to tell whether the jetliner might have been slammed from behind by a wall of wind as soon as it touched down.

The airplane's wheels showed no evidence of hydroplaning but apparently were rolling forward while also skidding slightly sideways. The runway was tested for skid resistance, and Black said the testers "described it as the best runway they had ever tested."