KINGSTON, Jamaica — Mystery shrouds the crash of a private plane carrying a prominent upstate New York couple who were taken on a ghostly 1,700-mile journey after apparently becoming incapacitated at the controls before slamming into the waters off Jamaica.

The wreckage of the high-performance plane carrying Rochester real estate developer Laurence Glazer and his entrepreneur wife, Jane — both experienced and enthusiastic pilots — had not been found late Friday, hours after U.S. fighter pilots launched to shadow the unresponsive aircraft observed the pilot slumped over and its windows frosting.

The plane’s pilot had indicated there was a problem and twice asked to descend to a lower altitude before permission was granted by an air traffic controller, according to a recording of the radio conversation. Radio contact with the plane was lost a short time later.

As dark fell, Jamaica Coast Guard Commander Antonette Wemyss-Gorman said search operations would be suspended and resumed at first light Saturday. A U.S. Coast Guard cutter was expected to arrive in the area late Friday and join the search at first light, said Petty Officer Sabrina Laberdesque.

Rick Glazer said that his parents were both licensed pilots. He said he could not confirm they were killed, adding that “we know so little.”

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 pressurization that causes the pilot and any passengers to pass out, he said.