A small plane with an unresponsive pilot crashed into the Gulf of Mexico on Thursday after circling erratically above the ocean for several hours.

The Cessna 421C landed softly in the water at 12:08 p.m. EST about 120 miles west of Tampa, Fla., and was floating upright until it sank, Petty Officer Elizabeth Boderland with the Coast Guard in New Orleans told The Associated Press.

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North American Aerospace Defense Command spokesman John Cornelio told the AP that two NORAD jets had flown with the aircraft for more than three hours before it went into the water, but had been unable to make contact with the pilot.

Crews flying over the crash site saw no evidence of survivors, according to the AP.

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The plane was flying from Slidell, La., to Sarasota, Fla., Federal Aviation Administration spokeswoman Kathleen Bergen told USA Today.

A Coast Guard cutter and rescue helicopter were en route to the crash site, CNN reported.

The Air Force began monitoring the plane after noticing it flying erratically over the Gulf of Mexico on Thursday morning, and planes sent up to investigate it reported the Cessna's windows were either iced or fogged over, Coast Guard Chief Petty Officer John Edwards told CNN.

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