DENVER, NOV. 16 -- Continental Flight 1713 was airborne for a "few seconds" Sunday before it yawed to the left, then to the right, clipped a wing on the ground and somersaulted into a snow-covered field between two parallel runways at Stapleton International Airport, officials said yesterday.
Witnesses on another jet landing on a parallel runway while Flight 1713 was taking off said the twin-engine DC9 was 20 to 50 feet off the ground before it began a forward cartwheel, its nose ramming into the grass as the tail followed the fuselage over in a flip, sliding 1,200 feet into a heap of wreckage.
Airline officials and investigators said they were mystified as to the cause of the accident, although investigators wanted to see whether ice buildup may have played a role.
Bruce Hicks, a spokesman for Continental, said the snowstorm was not serious enough to have caused the airline to shut down operations, and he said a review of the plane's mechanical record produced no immediate sign of mechanical problems with the jet. National Transportation Safety Board officials canceled an evening news briefing, saying they had no idea what to say.
The accident occurred so suddenly that the crew apparently did not have time to use the radio. Tape recordings of conversations between Flight 1713 and the control tower give no clue that the crew was in trouble, a Federal Aviation Administration spokesman said.
The jets' black boxes -- containing the cockpit voice recorder and flight-data recorder -- were recovered and reviewed quickly yesterday for any damage, then sent to the NTSB's laboratory in Washington for analysis.
Denver was in the midst of a snowstorm at the time of the accident, but airline and airport officials said flights were operating normally and no pilots complained of bad weather before Flight 1713's departure.
One of the passengers removed from the plane Sunday died today in a Denver hospital, bringing the total number of fatalities to 27, the airline said. Of the 55 survivors, 28 were still hospitalized, with 15 in serious or critical condition and the others listed as "stable" or better.
One survivor, Libby Smoot of Ketchum, Idaho, said all those aboard knew the flight was doomed when it wobbled violently just after leaving the ground. "We knew exactly what was happening," she said. "We were skidding on our side and eating dirt. A lot of people were screaming. A ball of flame passed by us as we were skidding along."
Given the horror of the scene, with the plane skidding nearly upside down along the snowy runway for about a quarter-mile, authorities were surprised and relieved that two-thirds of those aboard had survived. "It was luck, divine providence -- and the fact the airplane had not gained much altitude," said Dr. Norman Dinerman, associate director of emergency operations at Denver General Hospital.
Fred Farrar, an FAA spokesman, said the cloud cover was down to 500 feet at the time of the crash, and forward visibility was 2,000 feet. He said the winds were 10 knots -- about 12 miles per hour -- with peak gusts at 17 knots -- about 20 mph -- and the snowstorm was rated moderate.
He said the pilots were within the airline's minimum weather requirements for takeoff.
The jet had come in from Oklahoma City and had been scheduled to fly to Boise at 12:25 p.m. local time. But the flight was delayed to accommodate passengers from a canceled United Airlines flight. United officials said the flight was not canceled because of the weather, nor were any other United flights in Denver before the crash.
All the passengers boarded the plane in Denver and most of them were United passengers, said Hicks.
The jet pushed back from the gate at 1:20 p.m. and went to the airline's high-tech de-icing pad -- which operates like a carwash pouring a glycol mixture over the fuselage and wings.
Twenty-six minutes passed between the time of the de-icing and the time the jet began rolling down the runway.
Investigators said they are especially interested in determining whether ice buildup on the plane's wings affected its speed and engine performance. The 21-year-old jet, one of the older DC9-10 models, does not have slats on the front edge of the wing, and investigators are trying to determine whether the wing design could have played a role in impeding its takeoff.
The Douglas Aircraft Corp., which manufactured the plane in 1966, sent a notice to owners of the DC9-10 series in November 1985, warning them to be observant about how that model operates in icy conditions.
Douglas spokesman Don Hanson said that on the later models of the DC9 slats were added to the front, or leading edge, of the wing to give the plane additional lift on takeoffs.
In at least two other incidents a DC9-10 jet failed to take off in winter conditions. In February 1985, in Philadelphia, a cargo plane went down on takeoff. The crew survived and told investigators that one wing dropped and then the plane settled back on the runway.
In Sioux City, Iowa, in winter 1968, a DC9-10 lifted off, and the pilot retracted the gear. The plane rolled to the right and the pilot corrected it; it rolled to the left and the pilot again corrected it. But it then fell to the runway on its belly.
The older-model DC9s have been operated safely in severe winter conditions by many carriers for years, experts said. Hanson said the 1985 advisory was "nothing that hadn't been said before."
At the airport today, the fuselage lay upside down in the snow, its main landing gear pointed upward. Nearby was the cockpit, which had been crushed in the impact and severed from the main cabin just in front of the first-class seats.
Capt. Frank Zvonek, 43, and copilot Lee Bruecher, 26, were making their first flight of the day, Hicks said. Both were killed. Diana Mechling, the flight attendant who was killed, was sitting in the front flight-attendant jump seat. Two other flight attendants sitting further back survived.
The jet's tail section, also severed from the fuselage, lay about 300 feet away with the tip of its tail fin dug into the mud.
Between the tail and the runway was a trail of debris. Investigators said many of the dead victims were found in the debris path.
The plane, a DC9-10 model, the first of the Douglas DC9 series, had its last major service overhaul Oct. 27 and had flown 126 hours since then, Hicks said. He said "no significant" items needing maintenance work had been deferred.
Zvonek, a senior pilot with 12,000 hours of flying time, had been with Continental since 1969. He had endured Continental's prolonged pilot's strike in 1983 by opening a restaurant near San Diego. When the strike ended, he went back to work. Bruecher, who began working for the airline last July, had accumulated 3,200 hours of flying time and had an FAA inspector's license. The investigation by the National Transportation Safety Board was begun slowly because members of the board's "go team" were late arriving in Denver.
Several members of the team were in Detroit, where they were preparing for the first day of the board's public hearing about the Aug. 16 crash of Northwest Airlines Flight 255. By late afternoon, NTSB chairman Jim Burnett, who is heading the team, toured the crash scene and held a preliminary meeting with investigators.
The team was divided into subgroups to examine the jet's hydraulic and electrical system, its engines, the crew procedures, weather, and survival of the passengers.
"The most difficult thing so far was the getting here," Burnett said.