Coast Guard moves to the seabed after a Gulfstream air ambulance vanishes off Nantucket

Searchers off Nantucket are moving from the surface to the seabed for a Gulfstream G100 air ambulance that left Bermuda for Boston late on Friday and disappeared after 1 a.m. Saturday. Six people were on board. Four are Canadian citizens. Two are Bermudian. None had been publicly named by Sunday evening. A debris field has been found. No survivors have been reported.

The aircraft departed L.F. Wade International Airport on St David's Island at 11:41 p.m. Eastern time on Friday, FlightAware data cited by the New York Times shows. It was level at about 24,000 feet, then fell several thousand feet around 1:05 a.m. The Federal Aviation Administration lost contact and put out a search alert around 1:20 a.m. The Coast Guard was notified about 40 minutes later. Rear Admiral Matt Lake of the Coast Guard's Northeast District said on Sunday that crews had searched 2,840 square miles, about 7,356 square kilometres, with fixed-wing aircraft, helicopters, boats and cutters. The New York Air National Guard and Massachusetts authorities are in the search.

What the radio caught

Air traffic audio from the New York centre, carried by LiveATC and reported by the Boston Globe, has a controller asking the aircraft if it was "coming in blind," after an emergency call around 12:46 a.m. There was no further response from the cockpit. A later transmission recorded that the aircraft had lost radio and radar. Bermuda is one hour ahead of Eastern time. The airport operator, Skyport, said through spokesperson Ciara Eve that four crew and two passengers were aboard. Nantucket police checked the memorial airport and the island's southern shore and found nothing, Lieutenant Angus C. MacVicar said.

The FAA spokesperson on the alert was Rick Breitenfeldt. The plane was a medical flight, not a scheduled airliner. Air ambulances on the Bermuda-Boston run are a known night track for patients who cannot wait on a daytime commercial seat. The G100 is a small business jet used in that role. Six people on a medical flight usually means two pilots, medical crew, and a patient with an escort. The split released so far is four crew and two passengers, and four Canadians and two Bermudians. The two descriptions have not been matched in public. Families have not been named.

Why the search is dropping to sonar

A surface search of 2,840 square miles in 36 hours, Lake's figure, is a large box for a jet that left radar near Nantucket. A debris field narrows it. Debris on the water does not say where the airframe is, only that something from it reached the surface inside the box. The next step, which the Coast Guard described on Sunday and which Monday morning broadcasts were still reporting, is sonar on the ocean floor. Nantucket sits on a shelf. Depths south of the island are within the range of towed and hull sonar, and outside the range of a diver. A seabed search is a change of mission: from rescue, which the elapsed time has already made unlikely, to recovery and to a recorder if one can be found.

Lake called the area large and demanding. That is a fair description of a night descent from 24,000 feet with no further radio. The emergency call, the "coming in blind" exchange, and the loss of radar are the last three facts from the air. Everything since is on the water. The Canadian government has not, in the reports available Monday, published the names. Bermuda's airport has confirmed the headcount and the departure time, and stopped there.

What would close the file

The search closes, in any useful sense, when the seabed survey either finds the airframe or clears the box the debris field defines. A cockpit voice recorder or a flight data recorder, if this G100 carried one and if it is recovered, is the only source that can put the "coming in blind" call in a sequence: weather, a medical emergency in the cabin, a mechanical failure, or a loss of instruments. Until then the public record is the timeline. Wheels up at 11:41 p.m. from St David's. Level at 24,000 feet. A drop around 1:05 a.m. Radio and radar gone. An alert at 1:20 a.m. A debris field. Six people, still unnamed, and a sonar pass that has not yet been reported as finding the hull.