(Adds plane sank, pilot's identity)
April 19 (Reuters) - The unconscious pilot of a small private plane flew in circles over the Gulf of Mexico for hours on Thursday, shadowed by two U.S. military jets, before running out of fuel and crashing and sinking into the watery depths, authorities said.
The U.S. Coast Guard dispatched a plane, a helicopter and a Coast Guard cutter to the crash site, about 120 miles (193 km) west of Tampa, Florida, but the pilot did not emerge from the downed plane, according Coast Guard spokeswoman Elizabeth Bordelon.
The twin-engine Cessna landed gently and floated for a time, but then sank in the Gulf where the water is 1,500 feet deep (457 m), the Coast Guard said.
The plane took off from Slidell, Louisiana, en route to Sarasota, Florida, and ended up circling at 20,000 feet (6,000 metres), over Gulf waters, a Federal Aviation Administration spokeswoman said.
The pilot was Dr. Peter Hertzak, a gynecologist and cosmetic surgeon in Slidell, according to a spokesman in the mayor's office.
Two F-15 fighter jets sent up to intercept the Cessna because it was flying erratically said the pilot was "unresponsive," and the jets stayed with the plane, said Stacey Knott, a spokeswoman for the North American Aerospace Defense Command in Colorado Springs, Colorado.
Air traffic controllers had lost radio contact with the pilot at 9 a.m. EDT, and the military pilots sent to intercept were unable to reestablish contact. The plane crashed around three hours later, authorities said.
The command's mission is to prevent attacks and safeguard North American airspace, which may require it to "destroy platforms deemed a potential threat," it said in a statement. A command spokesman would not speculate on whether the plane would have been shot down if it approached land.
In a previous incident involving a "ghost plane," professional golfer Payne Stewart and five others died aboard a chartered private jet on Oct. 25, 1999. That plane lost cabin pressure, incapacitating those on board, and flew for four hours before crashing into a field near Aberdeen, South Dakota. (Reporting By Andrew Stern; Additional reporting by Jane Sutton in Miami; Editing by Vicki Allen and David Brunnstrom)