The pilot was the only person on the Cessna 421C. It went down Thursday about three hours after two F-15 fighter jets tried to make contact with the unresponsive pilot.
Coast Guard Chief John Edwards said the plane landed right-side up on the ocean surface and floating, but monitoring planes did not see a life raft deploy and never made contact with the pilot. The plane has since begun sinking into the Gulf about 120 miles west of Tampa, Fla.
A Coast Guard cutter and rescue helicopter are en route to the crash site.
