A small plane with its pilot slumped over flew a ghostly 1,700-mile journey down the Atlantic Coast shadowed by two US fighter jets before finally crashing in the waters off Jamaica.
The fate of the two or more people on board was not immediately known.
Major Basil Jarrett of the Jamaican defence force said the plane went down about 14 miles north-east of the coastal town of Port Antonio and the military dispatched two aircraft and a dive team.
"An oil slick indicating where the aircraft may have gone down has been spotted in the area where we suspect the crash took place," he said.
No wreckage has been located, but he said search-and-rescue teams were scouring the waters for any survivors.
The single-engine turboprop Socata TBM700, which took off from the Greater Rochester International Airport in New York en route to Naples, Florida, was carrying a prominent real estate developer and his wife, the couple's son said.
Rick Glazer said that his parents, Larry and Jane Glazer, were both licensed pilots. He said he cannot confirm they were killed, adding that "we know so little".
Larry Glazer ran the development firm Buckingham Properties. He owned the high-performance plane he was flying and was president of the TBM Owners and Pilots Association.
Public officials who knew the Glazers issued condolences centred on their role helping revitalise Rochester.
"The Glazers were innovative and generous people who were committed to revitalising downtown Rochester and making the city they loved a better place for all," said Governor Andrew Cuomo.
"I offer my deepest condolences to the Glazers' family and friends during this difficult and trying time."
The plane took off at 8.45am local time yesterday and air traffic controllers were last able to contact the pilot at 10am, the US federal aviation administration said. It added that it had not confirmed the number of people aboard.
At 10.40am, two F-16 fighter jets were scrambled from a National Guard base in South Carolina to investigate. They handed over monitoring duties around 11.30am to two F-15 fighters from Homestead Air Reserve Base in Florida.
US jets followed the plane until it reached Cuban airspace, when they peeled off, said Preston Schlachter, a spokesman for North American aerospace defence command & US northern command. FlightAware, an aviation tracking website, showed the plane over the Caribbean south of Cuba at about 2pm.
It finally came down after flying more than 1,700 miles.
On a recording made by LiveATC, a website that monitors and posts air traffic control audio recordings, the pilot can be heard saying, "We need to descend down to about (18,000 feet). We have an indication that's not correct in the plane." A controller replied, "Stand by."
After a pause, the controller told the pilot to fly at 25,000 feet. "We need to get lower," the pilot responded. "Working on that," the controller said
Controllers then cleared the plane to descend to 20,000 feet, a command which the pilot acknowledged. A couple minutes later, a controller radioed the plane by its tail number: "900 Kilo November, if you hear this transmission, ident" - identify yourself. There was no response.
According to FlightAware, the plane never carried out the last descent to 20,000 feet.
US fighter pilots observed the Socata's pilot slumped over before the turboprop's windows became frosted over, Mr Schlachter said.
On LiveATC recordings, the fighter pilots can be heard discussing the Socata pilot's condition.
"I can see his chest rising and falling right before I left," said one of the fighter pilots.
"It was the first time we could see that he was actually breathing. It may be a deal where, depending on how fast they meet them, he may regain consciousness once the aircraft starts descending for fuel ..."
The incident is the second time in less than a week that a private pilot has become unresponsive during a flight. On Saturday, a pilot lost consciousness and his plane drifted into restricted airspace over the nation's capital.
Fighter jets were also launched in that case and stayed with the small aircraft until it ran out of fuel and crashed into the Atlantic.
Cases of pilots becoming unresponsive while their planes wander the sky are unusual, with probably not much more than a handful of such incidents over the last decade, said aviation safety expert John Goglia.
Sometimes the incidents are due to a pilot becoming incapacitated by a heart attack or stroke, but more often the problem is insufficient cabin pressurisation that causes the pilot and any passengers to pass out, he said.
In 1999, the pilots of a Learjet carrying professional golfer Payne Stewart from Orlando, Florida, to Texas became unresponsive. The plane flew all the way to South Dakota before running out of fuel and crashing into a field.
Stewart and five others on board were killed. An NTSB investigation blamed the accident on depressurisation.