The U.S. Coast Guard is searching for a Gulfstream plane carrying six people that lost contact with flight controllers Saturday morning on its way to Boston from the island of Bermuda. The Coast Guard says air and surface teams launched a search for the plane, a Gulfstream G100 aircraft. The plane was conducting a medical evacuation in Bermuda, said Clarence Togeretz, director of flight operations for Latitude Air Ambulance, which operates the plane. “We are always very concerned when our crew does not inform us in a timely manner,” he told NBC News. “But I’ll say it again, optimistically and positively, that doesn’t mean the worst has happened.” Togeretz added that Latitude Air Ambulance has an emergency response plan for “absolutely anything that could happen to any of our missions.” The Massachusetts Port Authority, which operates Boston Logan International Airport, said the plane did not arrive as planned. A spokesman said: “Our thoughts are with those on board and their loved ones as the search continues.” Audio from the Boston air traffic control tower, obtained by NBC News, appears to indicate that controllers asked the plane if it was “coming in blind.” Controllers later ask another plane to “attempt to make contact” with the plane. It is unclear whether that attempt was successful. The current search area is “off the coast of Nantucket,” the Coast Guard Northeast District said in an update to Data from Flightradar24 showed a number of aircraft searching south of the island. The Federal Aviation Administration said in a statement that it issued a search and rescue advisory for the plane at 1:20 a.m. ET on Saturday, and is coordinating with the Coast Guard and the Rescue Coordination Center to locate the plane. Bermuda is a British overseas territory in the North Atlantic, about 650 miles from North Carolina.