So thick was the cloud cover over Linden, N.J., on Friday morning that a veteran pilot from Bethesda was advised to scrub the flight that ended minutes after takeoff in a fiery crash. The pilot, his wife and his daughter were killed, and 25 people on the ground were injured.

The director of the Linden Municipal Airport said that Itzhak O. Jacoby, 53, a pilot with 20 years' experience flying and teaching flight, ignored a basic rule of thumb taught to private pilots: Never take off from an airport where foul weather would prevent you from landing immediately in an emergency.

A few miles from the airport, the single-engine 1964 Beech Bonanza 35 smashed into a Newark neighborhood, hitting the top floor of an old factory, slicing open cars and breaking into pieces in the parking lot of a fast-food restaurant. Two people remained hospitalized in critical condition yesterday, and by afternoon two streets were still closed for the cleanup.

Police said the factory, which caught on fire, had to be demolished, and the Associated Press reported that the city has asked the State of New Jersey for $1 million for the cleanup.

With a half-mile of visibility and zero cloud ceiling, landing conditions were much poorer than federal regulations permit at the Linden airport. Pilots would not have been allowed to land, even if they could see, said Paul Dudley, director of the Linden airport. There are no such regulations for takeoffs, so Jacoby didn't violate rules in beginning his flight to Dulles International Airport with his wife Gail, 50, and their daughter Atira, 13.

With no one else taking off or landing, sea gulls and geese had begun to congregate on the warm runway pavement. Jacoby asked airport personnel to shoo away the birds. Two members of the airport staff advised Jacoby to postpone his flight, "but he said there was not a problem, he had to go," said Dudley, whose staff recounted the exchange to him.

"He certainly did something we consider inadvisable," Dudley said. "He didn't have the ability to turn around and get back on the ground because he couldn't see."

One minute after takeoff, Jacoby radioed that the plane was in trouble, and he radioed twice more to report problems with the gyroscope, which helps keep the plane level, according to investigators from the National Transportation Safety Board.

Investigators said yesterday that they do not know what caused the crash. At this stage in the investigation, they have not indicated that hazardous landing conditions at Linden were a factor.

Investigators are studying the gyroscope but will need months to determine whether the device was to blame, or foul weather, or some combination of factors.

Doug McNeeley, a friend of Jacoby's and the manager of the Montgomery County Airpark, where Jacoby did some teaching, took exception to Dudley's analysis of Jacoby's decision to fly.

Although confirming that young pilots are taught not to take off from airports that are socked in, McNeeley pointed out that many components go into the decision to fly. Jacoby was an extremely competent pilot in all weather, and he had a well-equipped plane. He knew that much larger Newark International Airport was near.

"It was his decision, and I'm confident with his credentials and his experience, if he felt it was safe for him to take off, then it was safe for him," McNeeley said.

Jacoby was a director at the Uniformed Services University of the Health Sciences. Gail Jacoby was an administrator at the National Institute on Aging. Atira Jacoby was a freshman at Walter Johnson High School. They were returning from a Thanksgiving visit with an older daughter, Orit Jacoby, an architect who had recently married and lives in New York.