The first time Bonnie Seidle saw the plane she was sure it was in some kind of trouble. There were aircraft flying over her home in a small subdivision near Waldorf all day long, but she had never seen on this big flying this low.

The second time that the C-130 cargoplane with its camoufage colors, its massive belly and its 132-foot wingspan circled the nighborhoo around Elsa Avenue, Sue Gardner was convinced that the wings would shear off the roof of her small suburban home.

A few miles away on Route 228, a pair of school buses bearing children home on Tuesday afternoon stopped abruptly, as terrified drivers and children watched the plane approach.

"He was at the tops of the treeline, at telephone poles, right over the roofs of the houses," said bus driver Jessie Matthews. "I got my radio and told the bus ahead of me to stop, then I just folded my hands and started praying," she added.

According to officials at Andrews Air Force Base, the huge four-engine Lockheed Hercules cargo plane -- a model once used to carry troops and heavy equipment into battle in Vietnam -- left the base early Tuesday afternoon with a pilot and crew of four.The five men intended to do some "proficiency flying" to log extra hours in the air as part of their training, the officials said.

For as many people in the Shady Acres subdivision of Waldorf and the semirural area surrounding Elsa Avenue, however, the flight of the Air Force reservists was less an exercise in proficiency than an exercise in panic. The region is about 30 miles southeast of Washington.

Varying accounts from residents alongElsa Avenue say the plane circled the area between three and 10 times, passing so low that young children screamed with fright at the noise of thefour propellers.

An older resident of the neighborhood, Delores Phillips, said she has not been able to sleep since the afternoon when the sight of the plane sent her crouching behind the washing machine on her porch, afraid that the aircraft was about to slam into her roof.

"I could see two people in the plane," said Mrs. Phillips, a woman in her 50s who has suffered a heart attack. "I've never seen a plane that big coming right at me.

"When I hear a plane now, I just get a cold chill," she said.

Lt. Col. Bob Thatcher, a spokesmanfor Andrews Air Force Base, said yesterday that a C-130 cargo plane, part of the 459th Tactical Airlift Wing -- an Air Force Reserve unit --was flying in the vicinity Tuesday afternoon but had no authorization to fly at low altitude over that particular neighborhood.

"It had been flying its normal low-level route, its published route, south of Waldorf," said Thatcher. "Then hecame back to the base, discharged his pasengers, and went back up to do some proficiency flying."

Thatcher, who said he did not now thename or rank of the pilot, said the incident is being investigated by Brig.Gen. Charles E. Jones III, commander of the 459th. The investigation, which began "as soon as the first calls came in," should be completed by next week, and its "results will be made public at that time, Thatcher said.

An official at the Charles County sherif's office, where emergency "911" calls are received, told Mrs. Seidl that 30 emergency calls came in during a 15-minute period at midafternoon Tuesday. The officer in charge of that division, however, could not be reached yesterday and Lt. Donald Poole said there were no written reports made on the incident.

Likewise, officers at the Waldorf barracks of the Maryland State Police were unfamiliar with the incident.

And at least one resident of Elsa Avenue said she did not think that the cargo plane posed a threat to her home and family. "We're in the path of a lot of aircraft," said Faith Mesenbourg. "People are getting hysterical over nothing," she said.

Karen Kettig, who lives at the otherend of the small road was not so sanguine when she saw the plane circle twice low over the treetops. She persuaded her husband Bob to drive her and their three-year-old son Evan away from the neighborhood until the plane left. They drove around for nearly half an hour before deciding to return home.

"I've got four very large show horsesin my back yard, and they were bouncing off the fences and each other, they wereso scared," said Seidl. "They were lathered up for four hours afterward."

"The finale was that he (the pilot) went down to the end of the street and lined it (the plane) up like he was parallel to a runway and came through like he was going to set that plane downon our street. I have never been so terrified in my life."

"I guarantee you we're investigating this very, very hard," Thatcher said yesterday. "We're not here to frightenor terrorize anyone . . . all the people who work at Andrews live in the communities around here."

Riding on Jessie Matthew's bus was another Elsa Avenue resident, 14-year-old Barry Moore. "There weresome girls on the bus screaming," he said. "The bus driver was telling us to shut up."

Barry's neighbor, Leona Marchese, declared, "I didn't know what to do, I was so frightened. I didn't know whether to duck or run or what. It was so big, it looked like a huge shark above me."