ROMULUS, MICH., AUG. 19 -- The cockpit crew of Northwest Airlines Flight 255 apparently forgot to set the aircraft's wing flaps when preparing to take off from Detroit's Metropolitan Airport Sunday, creating a plane that was nearly impossible to fly because it was fully loaded, sources investigating the jetliner's fatal crash said today.

Federal safety officials examining preliminary readings from the airliner's flight data recorder said they were shocked at the apparent omission. Turning wing flaps down to aid in takeoff is one of the most basic procedures in commercial aviation.

"At first we didn't believe it because it's just too horrifying," said one official involved in the investigation of the nation's second-worst air disaster, which killed at least 156 people when the jet slammed to earth after rising only 48 feet above the airport's runway 3C. "But it looks like they completely forgot to set them."

John K. Lauber, the National Transportation Safety Board member leading the investigation, said tonight at a news conference that while it is technically possible to have flown the plane during takeoff with the flaps retracted, it was "highly unusual" for the flaps to be up.

He added that during the routine preflight check the pilots apparently forgot to call out the flap position. "We can hear items being called on the checklist on our audio tape," Lauber said. "But there was no mention of flaps at all."

The failure to complete a routine preflight check of how the plane's instruments were set for the flight is an apparent violation of federal law and airlines' operating procedures.

Investigators said tonight, however, that they heard no sign on the tape of a warning to the crew that their flaps were not down. The investigators said the craft was equipped with such a warning device but that it may not have been working.

Neither member of the crew had any history of absenteeism, unusual sickness or problems on the job, Lauber said tonight.

One investigator said that, according to preliminary information taken from the jetliner's flight data recorder, which registers detailed performance characteristics of the plane, the flap readings were "set at 0-0. Nothing."

The flaps assist in lifting a plane into the air at slower speeds or on shorter runways. If the flaps are not extended, higher speed is required for the plane to achieve flight. If flaps are used for takeoff, they are routinely retracted after the plane has reached preliminary cruising speed.

The NTSB reported tonight that preliminary airspeed data indicated that the plane was traveling between 142 and 149 knots at liftoff and reached a maximum speed of 184 knots before crashing. Lauber said it is not yet possible to tell whether that speed was sufficient.

The preliminary assumption of federal investigators is that the crew members computed a takeoff speed that assumed a flap setting, then failed to set the flaps. When they reached what they thought was takeoff speed, they lifted the nose into the air.

"It looks like the airplane didn't want to fly," a federal source said. The NTSB said that witnesses have reported the plane attempted to climb at an unusually high angle. "That's the tendency," the source said. "You have no choice but to try and climb out of it, but if there is not enough airflow over the wings {because of the absence of flaps}, you will lose it altogether." That would be a stall, and it is known the aircraft's stall warning sounded in the cockpit.

"It doesn't look like it was a very well-coordinated preflight and departure from a crew standpoint," a federal source said.

Northwest officials declined to comment on the reports of pilot error this evening, saying that they had not yet seen the data recovered from the aircraft.

At the briefing tonight, Lauber said that the investigation so far suggests that there was no severe weather on takeoff, that the plane was not overloaded with baggage and that there was no engine fire.

Yesterday, officials of the NTSB said that the craft's pilot, John Maus, a 32-year veteran with more than 7,000 hours in the cockpit, had no penalties.

They also said that First Officer David Dodds, 35, a Northwest employe for eight years, had had only one minor violation in his career.

Sources cautioned today that the information was sketchy because it was based on the first full reading of the cockpit instruments that measure the aircraft's performance. But they added that they were confident of the quality of the tapes.

"It's just an incredible tragedy," said one official involved in the investigation, who said he was stunned by the revelations. "But we have to see everything in black and white before we can make any final assessments."

The next step in the investigation will be to match the information on the flight data recorder with whatever control settings were recorded on the cockpit voice recorder as the crew went through its preflight checklist. Settings for flaps and other controls would normally be called out by one crew member and repeated by the other.

Because eyewitnesses had reported seeing a ball of fire near the left engine before the plane hit the ground, early scrutiny was devoted to the condition of the engines.

Today, investigators all but ruled out engine failure as causing the accident at 8:46 p.m. Sunday.

However, sources said, there are several possible explanations for the flames many witnesses have said they saw coming from the left engine. One could be a turbine compressor stall, much like an automobile backfire, that would occur because airflow to the jet engine was blocked by the high angle of the wings on the plane.

Another possibility, a source said, is that a fuel tank in the plane's wing was ripped open by a light pole while the plane was still airborne and spewed fuel back into the engine. "We just don't have all the events and the time sequences worked out yet," the source said.

Safety board member Lauber called today for amateur meteorologists to provide investigators with relevant data. But sources said that low-level wind shear alerts that were reported at the airport about 35 minutes before departure did not appear to contribute significantly to the accident.

The confusion about the death toll in the crash continued. Northwest said that 154 of the 155 people on the aircraft died in the crash.

But safety board officials said again today they think that the figure is 153.

Only 4-year-old Cecilia Cichan of Tempe, Ariz., survived the crash. She was reported in serious condition today at C.S. Mott Children's Hospital in Ann Arbor, Mich.

The Wayne County sheriff said that it is not yet possible to identify all the remains to determine with certainty how many motorists died when the plane hit cars.

This afternoon officials removed both engines from the roadway where the jetliner crashed and took them to a hangar at the airport. Within the next week. the Pratt and Whitney engines will be taken to the manufacturer's research facility in East Hartford, Conn., for closer inspection. Staff writer Douglas B. Feaver contributed to this report.