A United Airlines Boeing 737 crashed nose-down into a park yesterday as it approached the Colorado Springs Airport in strong, gusty headwinds and low-altitude turbulence, killing all 25 aboard.

Witnesses said the plane banked sharply to the right and turned nearly straight down into the long, narrow park, which has a number of playgrounds and running trails. It exploded on impact into little more than shards of metal and smoldering debris, the witnesses said. Fewer than a half-dozen identifiable pieces of wreckage were left, the largest being a landing gear assembly.

Except for a few broken windows, nearby apartment buildings and houses were spared. The only known injury on the ground was to a small girl standing in a doorway, who was knocked backward by the force of the explosion and hit her head. She was released from a local hospital after treatment.

Witnesses said the park would have been filled with children on a weekday but is usually empty on Sunday mornings. The crash occurred about 9:55 a.m.

"Most of the kids go to church around here," said Margaret Fine, whose apartment overlooks the crash scene. "Thank God it happened today and not yesterday. There were a zillion kids playing in the park yesterday." She said the jet passed so low over her apartment that she ran to a window just in time to see it hit.

"We heard this horrible noise

and saw a shadow," she said. "It's like darkness came over our house."

United Flight 585 was completing a short hop from Denver after a flight that originated in Peoria, Ill., with a stop in Moline. Twenty passengers and five crew members were aboard, a light load for the Boeing 737-200. The plane had 109 seats. The National Transportation Safety board dispatched a team to the site from Washington, led by board member John K. Lauber.

The cause of the crash may not be known for months as the board investigates, but sources said one focus of the probe will be on whether it was the nation's first major crash related to wind shear in six years, perhaps in combination with a mechanical problem.

Aviation sources said pilots had reported severe low-level turbulence all morning at Colorado Springs, as gusty northwest winds swirled down the front range of the Rocky Mountains.

On the ground, winds appeared normal under clear, springlike skies. But pilots landing at the airport had made several "urgent" reports of severe turbulence at levels of 150 feet to 400 feet above the ground, as well as at higher altitudes. "It was moderate to severe all over the place," said one source.

About 30 minutes before the crash, another 737 pilot reported sudden surges in air speed of nearly 40 mph below an altitude of 400 feet.

However, airline sources point out that such conditions are common enough in the area that pilots usually would be expected to handle them, particularly pilots for United, which has a major hub at Denver and which has been a leader in wind shear survival training.

The last major U.S. wind shear crash occurred Aug. 2, 1985, when Delta Flight 191, a Lockheed L-1011, crashed at Dallas-Fort Worth International Airport, killing 137.

Sources said that if wind shear was a factor yesterday, it was probably not a microburst, the most severe form. Instead, they said, it might have been a phenomenon common in the West -- strong winds a few hundred feet above the ground combined with a pocket of calm air lower down. A plane emerging suddenly from a strong headwind into calm air might drop uncontrollably.

The 737-200 is an older version of the twin-engine jet, the world's largest-selling airliner. Nearly 1,100 of the 737-200 model were built between 1968 and 1988.

Lawrence Nagin, United senior vice president, said at a news conference at company headquarters in Chicago that the plane had no history of problems. Nagin said United bought the plane in June 1986. It was delivered to the former Frontier Airlines in 1982. According to the Associated Press, Nagin said the aircraft was "relatively young" with 26,000 air hours and 19,734 flights.

Officials from the Denver field office of the National Transportation Safety Board arrived at the scene about five hours after the crash. Captain Dave Bachrach of the Security Colorado Fire Department said law enforcement personnel had secured the site for board investigators. One "black box" recorder had been found, officials said.

Bachrach said some human remains had been recovered, but Capt. Howard Schafer of the El Paso County Sheriff's Department said most of the bodies were believed "compressed into the fuselage, about 20 to 30 feet down."

Many witnesses to the crash were sitting in parkside apartments. None mentioned seeing any obvious problems before the crash, such as smoke or an explosion.

Larry Abegglen, whose house is about 300 yards from the crash site, said he was watching television "when I caught something out of the corner of my eye. I looked out the living room window and saw the plane roll over on its right side and go into the ground."

Abegglen said he ran across the street and joined his neighbor, jumped a fence and started running across the park to the site.

"I ran less than 60 yards into the park when I saw body parts. That was enough for me, I stopped right there," Abegglen said. He said he realized no one could have survived.

Like several other witnesses, Abegglen said the wind suddenly became gusty on the ground right after the crash, blowing debris around. Baerbel Sapp, whose house is on the park, said, "The wind came up suddenly. Everything started flying. It lasted about two minutes."

"There are lots of planes that come over here," said Fred Blair. "It's normal. But I thought this one was really close. The engine sounded like a screwdriver sounds when stuck in a radiator fan. I thought I was going to die. I ran to the door right as it hit nose first. The entire plane disappeared in one one-hundredth of a second."

Special correspondent Michael B. McPhee contributed to this report from Colorado Springs.