While much attention is directed at US Airways Flight 1549, other NTSB investigators continue to probe the crash of a Continental Boeing 737-500 (N18611) at Denver International Airport (DEN) on Dec. 20.

Continental Flight 1404 was taking off for Houston's Bush Intercontinental Airport (IAH) when the accident occurred. The jetliner was substantially damaged after the flight deck crew tried to abort the takeoff, exited the runway and ended up in a ravine in flames. The plane carried 110 passengers. Thirty-seven people were injured, but there were no fatalities.

The NTSB said there were 24-32 knot crosswinds at the time, fueling speculation that weather may have played a role in the accident. But an NTSB spokesman said that the crosswinds were not so strong that the pilot would not have been able to take off.

So, other factors, such as mechanical failure or pilot error, are being eyed.

The Boeing jetliner equipped with CFM56-3B1 engines departed the left side of Runway 34R. Inspection of the runway following the accident revealed that it was bare and dry and free of debris. The first tire marks were found about 1,900 feet from the runway threshold. The aircraft exited the runway at about 2,650 feet from the runway threshold, continued across a snow-covered grassy drainage basin area, and crossed a taxiway and a service road before coming to rest about 2,300 feet from the point at which it departed the runway.

On the night of the accident, the majority of air traffic was arriving at the airport from the south and departing from the airport to the north.

Both members of the flight deck crew have been interviewed. The injured captain, who was in control of the aircraft, had accumulated a total of about 13,000 hours, with about 5,000 in the 737. The first officer had flown about 7,500 hours in his career with about 1,500 hours in the 737.

The NTSB said both pilots were aware of the crosswind conditions, having been advised by Air Traffic Control (ATC) that winds were 270 degrees at 27 knots just prior to takeoff.

The weather observation (METAR) in effect for DEN nearest the time of the accident was reported to be winds at 290 degrees and 24 knots with gusts to 32 knots, visibility of 10 miles, a few clouds at 4000 feet and scattered clouds at 10,000 feet.

The temperature was reported as -4 degrees Celsius. Wind data was obtained from the airport's low-level wind shear alert system (LLWAS), consisting of 32 sensors located around the field, which record wind speed and direction every 10 seconds. (This information will be used to determine a better estimate of the actual crosswinds at the time of the accident.)

"Both pilots remarked that all appeared normal until the aircraft began to deviate from the runway centerline. The captain noted that the airplane suddenly diverged to the left, and attempts to correct the deviation with the rudder were unsuccessful," the NTSB said.

The caption stated that he briefly attempted to return the aircraft to the centerline by using the tiller to manipulate the steering of the nose gear but was unable to keep the aircraft on the runway.

Mysterious 'bumping and rattling' sounds audible on the Cockpit Voice Recorder (CVR) have been time- correlated with the Flight Data Recorder (FDR) and were found to have occurred as the airplane exited the runway and traveled through the grassy areas adjacent to the runway. The aircraft reached a maximum speed of 119 knots, and it was traveling at 89 knots when the CVR and FDR stopped recording.

Two Continental pilots who had flown the aircraft into Denver on the previous flight were passengers on the accident flight. Neither of the pilots noted any anomalies on the inbound flight and reported that all the aircraft's systems had operated normally.

The airplane's Quick Access Recorder (QAR) and other electronics were retrieved and sent to the NTSB laboratory in Washington. The QAR, which records aircraft data, often has more parameters or information of higher fidelity than the FDR. Additional items, such as flight control and nosewheel steering actuators, were also removed from the airplane for testing and evaluation.

Physical inspection of the engines and information from the FDR has not indicated any evidence of pre-impact malfunctions with either engine. The FDR data shows that No. 1 engine power was reduced before that of the No. 2 engine during the accident sequence. Examination of the engine indicates that this reduction is consistent with snow and earth ingestion as the airplane departed the runway.

The FDR data also shows that both engines were commanded into reverse thrust following rejection of the takeoff by the flight crew, which occurred after the aircraft had already left the runway.

A preliminary examination of the rudder system revealed no abnormalities or malfunctions. The main landing gear and brakes, which had separated from the aircraft during the accident sequence, were found in good condition by visual examination. There were no signs of hydraulic leaking or flat spots on the tires. The flight deck controls and corresponding control surfaces were found to be in the takeoff configuration.

It could take as much as a year for the Safety Board to close its investigation of Continental Flight 1404.