In a chilling midsummer tragedy that made overnight headlines around the world and quickly put the Vineyard beneath the harsh spotlight of the national media, a small airplane flown by John F. Kennedy Jr. plunged into the Atlantic Ocean off the western end of the Island on Friday night.

As of yesterday, Mr. Kennedy, 38, his wife Carolyn Bessette Kennedy, 33, and her sister Lauren Bessette, 34, were all missing and presumed dead. Numerous small pieces of the wrecked plane had washed up along the south shore of the Vineyard. On Sunday night the National Transportation Safety Board formally opened an investigation into the incident as a plane crash.

A massive search and rescue mission launched by the Coast Guard on Saturday was changed to a search and recovery mission on Sunday night, when leading Coast Guard officials announced grimly that they no longer had any hope of finding survivors in the 68-degree ocean water.

“I have just talked to the Kennedy family and it was a very difficult phone call. We are in the business of saving lives and anytime we have to do this it isn’t easy,” said Adm. Richard Larrabee in a press briefing Sunday night.

In an especially sad irony, some wreckage from the plane washed up a short distance from the shorefront of the nearly 400-acre Kennedy family estate off Moshup Trail in Aquinnah.

The Dukes County Search and Rescue Team, an all-volunteer, specially trained team of Island citizens, led a massive weekend search along some 20 miles of shoreline, from the Aquinnah side of the jetties in Menemsha all the way to Chappaquiddick. The search has been both on foot and by all-terrain vehicles.

Massachusetts Environmental Police Sgt. Bill Searle said yesterday that debris believed to be from the Kennedy plane has been recovered as far east as the Edgartown Great Pond and as far west as the bowl under the Gay Head Light.

Reached by telephone last night during his first break in some 47 hours, Mr. Searle said the search team was still working at full tilt.

“This has been a phenomenal cooperative effort at a local level,” Mr. Searle said. “I think the Island under times of stress and grief, it brings something out in people. And the question is always, ‘What can I do?’ That is what we have heard, not just from every agency, but from stores and other people straight across the board. It wasn’t a matter of, ‘If you need me, I’ll show up.’ They just showed up,” he said.

The local search effort on the ground over the weekend involved a wide array of local officials in addition to the search and rescue team, including police and fire departments in all three up-Island towns, the Edgartown police, the Edgartown parks department, the Dukes County Sheriff’s Department and rangers from The Trustees of Reservations and from the Wampanoag Tribe.

Mr. Searle said volunteer efforts have extended far beyond local officials and include many Island residents and merchants who have reached out to assist in countless ways. Local businesses have sent food and water to the search and rescue workers, who have been on the beaches from well before sunup until well after sundown for three straight days.

“I can’t say strongly enough how amazing this Island has been in a time of need,” he said.

Singled out for special praise by Mr. Searle was Bart Cook, a ranger for the Trustees who is a senior team leader with the search and rescue team. Mr. Searle is the rescue team leader.

Mr. Searle said the shore search included a core team of 35 to 40 men and women and seven all-terrain vehicles. He said the search will continue until he receives instructions to the contrary from the unified command center at Otis Air Force Base.

“I would say we are going to continue to search but at a reduced effort, not because we don’t care but because we don’t have the local resources,” Mr. Searle said.

A massive search is also under way on the water using, among other things, Coast Guard salvage vessels and Rude, a research vessel from the National Oceanic and Atmospheric Administration equipped with side-scan sonar.

On Sunday night Admiral Larrabee said the water search had identified two potential targets where state police dive teams would be deployed for further search, but he emphasized that they were only potential sites. No new real information was released yesterday about the results of the water probe.

The intensive bottom search is now concentrating on a 24-square mile area west and southwest of the Vineyard, including the waters around Noman’s Land. Charted water depths in the search area are 80 to 130 feet. The massive search and rescue mission which went on throughout the weekend initially covered an area of some 9,000 square miles from Martha’s Vineyard to Long Island.

By Gazette press time yesterday, the accident had been reported exhaustively by virtually every print and broadcast media outlet in the country, and many international outlets as well. Members of the media descended on the Vineyard in force on Saturday afternoon in a scene that is now familiar to Island residents.

Early on Saturday, no one was in charge of information at the Martha’s Vineyard Airport, and the result was considerable confusion. The airport manager was unavailable, and when the story broke early in the day, all calls to the airport from the press were referred to a telephone number in Washington, D.C. The number turned out to be Sen. Edward Kennedy’s office.

The confusion subsided when West Tisbury police chief Beth Toomey stepped in to help provide order at the airport, but chaos returned later in the day when a mainland state police captain came in to handle public information.

Local officials were moved aside, and press conferences were held every three hours, but little real information was available. Off-Island state police who were assigned to manage public information appeared to be poorly informed about even the most basic facts, including marine and geographic information pertaining to the Vineyard. Agitation grew among members of the press.

Meanwhile, leading Coast Guard officials staged regular press conferences in Boston with detailed information about the search and rescue mission under way on the water.

On Sunday it was announced that a unified command post had been set up at Otis, with the Coast Guard and the National Transportation Safety Board leading the command efforts. The unified command also included civil air patrol and state police.

In the official account of events to date, Mr. Kennedy, his wife and sister in law left from Essex County Airport in Fairfield, N.J., at about 8:45 p.m. Friday aboard his single-engine Piper Saratoga HP. Mr. Kennedy was considered a novice pilot and had purchased the plane in April.

The plane was due to arrive at the Martha’s Vineyard Airport at about 10 p.m., and it was later reported missing after some Bessette relatives had apparently gone to the airport to meet the plane. Mr. Kennedy reportedly planned to drop Lauren Bessette off on the Vineyard, and he and his wife were to continue on to Hyannis. A family wedding for Rory Kennedy, the daughter of the late Sen. Robert Kennedy, was planned for Saturday afternoon at the Kennedy family compound in Hyannisport.

Mr. Kennedy’s plane was tracked by Federal Aviation Administration radar on its final approach to the Vineyard. The plane’s last position on FAA radar was 17 miles west-southwest of the airport and about six miles from shore. Early reports from the FAA about the plane’s altitude at the time of the last radar contact were revised late yesterday. Officials said the plane had made a precipitous drop of 1,100 feet in 14 seconds - a much sharper drop than previously reported.

At 2:15 a.m. on Saturday, a family friend notified the Coast Guard in Woods Hole that the plane was late. Early Saturday morning a search was launched off Long Island, but the probe was later moved to the area off the Vineyard.

A short time after the search was narrowed to the waters off the Vineyard, pieces of wreckage were found in the water about 100 yards off Philbin Beach, including a wheel and a suitcase with Lauren BessetteÕs name on it.

Although the intensive search continued yesterday, some of the frenzy had subsided.

“This has been a media event of biblical proportion, but I’ve been doing this long enough that I know tomorrow will come,” said Chilmark police chief Timothy Rich.

Residents and officials alike paused to reflect on John F. Kennedy Jr., who, like his sister, Caroline Kennedy Schlossberg, and his late mother, Jacqueline Kennedy Onassis, was a quiet presence on the Vineyard. Mrs. Onassis bought her Aquinnah property from the Hornblower family in 1978. After she died five years ago, the property was inherited by her two children.

“I drove all the way up-Island today and it was a good exercise in understanding that life goes on,” said West Tisbury Chief Toomey late yesterday. “It reminded me very much of John [Kennedy Jr.], of how life would go on when he would come here - he would be very low profile and life would go on around him,” she said.

“It was a special family - they kept such a low profile here and I really respect them. This is a loss.”