Authorities on Sunday suspended the search off the Massachusetts coast for six people on an air ambulance that disappeared during a flight from Bermuda to Boston. The U.S. Coast Guard said searchers covered more than 4,400 miles over a span of 66 hours for the four Canadians and two people from Bermuda who were on board.

"Suspending a search is not an easy decision," Rear Adm. Matthew Lake, commander of the Coast Guard’s northeast district, said in a statement. "We express our deepest condolences to the families and loved ones affected by the tragedy and our gratitude for our partner agencies who helped support search efforts."

The Federal Aviation Administration contacted the Coast Guard at 2 a.m. Saturday after losing contact with the Gulfstream G100 aircraft over the Atlantic Ocean. Searchers later Saturday discovered a "debris field" off the coast of Nantucket, Lake stated during a news conference on Sunday.

Coast Guard crews, along with the New York National Guard’s Air Rescue Wing and Massachusetts authorities, searched a vast area using fixed-wing aircraft, helicopters, boats, and cutters. The depth of the water around the debris field ranged from 80 to 90 feet.

The Canadian-registered air ambulance jet had four crew members and two passengers when it departed Bermuda’s L.F. Wade International Airport for the nighttime flight to Massachusetts, according to a statement from the Bermuda airport’s operator, Skyport.

Air traffic audio suggests the plane may have been "coming in blind" as a storm approached shortly before it vanished. The pilot reported electrical problems and declared an emergency as the jet neared the coast, according to air traffic control audio posted by LiveATC.net. A controller can be heard asking the pilot, "Roger, you said you’re coming in blind. Is that what you said?"

Mary Schiavo, a former Inspector General of the Transportation Department and aviation attorney, suggested that the plane might have lost its navigational instruments as a storm moved across its radar path. Preliminary data from flight tracking site FlightRadar24 indicated the plane descended sharply from its cruising altitude of approximately 24,000 feet to around 10,000 feet.

"Something bad happened with this big drop, and they flew into this big storm. It’s a terrible place to have a loss of your instruments and be flying blind," Schiavo said. "It’s very easy to get disoriented and not know if you’re turning, climbing, descending, etc."