A medical transport jet carrying six people disappeared Saturday while flying from Bermuda to Boston, prompting the U.S. Coast Guard to launch an air and sea search off the coast of Nantucket.

The Gulfstream G100 air ambulance departed L.F. Wade International Airport in Bermuda early Saturday morning bound for Boston Logan International Airport. The Federal Aviation Administration lost contact with the aircraft during the flight and issued a search-and-rescue alert around 1:20 a.m. The plane was carrying four crew members and two passengers, according to Bermuda airport officials. It is registered in Canada and operated by Latitude Air Ambulance, based in Hamilton, Ontario.

The Coast Guard said the search area is off the coast of Nantucket, Massachusetts. Multiple units have been deployed, including aircraft from Air Station Cape Cod, an MH-60 helicopter, a 47-foot motor lifeboat from Station Brant Point and the USCGC William Sparling. Both air and surface crews are involved.

The aircraft was expected to arrive at Boston Logan early Saturday but never reached the airport. Massachusetts Port Authority officials said the plane did not arrive as scheduled and expressed concern for those aboard and their families. Flight-tracking data indicates the aircraft had been flying at roughly 24,000 feet before a rapid descent and loss of contact, though authorities have not publicly determined the cause.

The National Transportation Safety Board is gathering information while the FAA and Coast Guard continue coordinating the search-and-rescue operation. Officials have not released the identities of those aboard or confirmed what happened to the aircraft. The search remained active Saturday