Unresponsive Plane Crashes in Gulf of Mexico

April 19, 2012 -- A twin-engine aircraft crashed into the Gulf of Mexico after the pilot was unresponsive for nearly three hours as radar tracked the plane flying aimlessly in loops.

The FAA lost radio contact with the Cessna 421 before 9 a.m. ET. It was circling at approximately 28,000 feet. Fully loaded, the plane was carrying about 3.5 hours worth of fuel. Only the pilot was thought to be on board.

The plane took off from Slidell, La., and was en route to Sarasota, Fla., according to a flight plan. Somewhere between the two points, it began flying in circles.

Officials at NORAD confirmed that the air defense agency has launched two F-15 fighter aircraft to intercept the general aircraft over the Gulf of Mexico.

NORAD spokesman John Cornelio said the fighter jets made contact visual with the aircraft over the Gulf around 8:45 a.m. They monitored the situation providing overhead cover.

"We are monitoring the flight pattern and the aircraft remains unresponsive," said Cornelio before the crash.

In addition to the Air Force F-15s, the Coast Guard has dispatched an HC-144 ocean sentry airplane from Mobile, Ala. An NH-60 Helicopter is on stand by in Clearwater, Fla. The US Coast Guard Cutter Coho was en route.

Spotter aircraft confirm the plane landed right side up and did not break apart, but later began to sink, according to the Coast Guard.

The Coast Guard has asked mariners in the area to offer assistance.

The pilot may have suffered hypoxia,or a lack of oxygen, said ABC News aviation consultant Stephen Gaynaard.

"As the pilot was in the climb, the cabin was not pressurizing," he speculated, "so there was not sufficient oxygen to keep him conscious."

The plane appears to have been flying between 10,000 and 30,000 feet after the pilot became unresponsive.