A Cessna plane bound for Fort Lauderdale Executive Airport crashed Friday evening more than 300 miles off the coast of Florida after air traffic controllers lost communication with the plane and fighter jets were sent to investigate, the authorities said.

The pilot of the Cessna Citation V is believed to be the only person who was on the plane, the Federal Aviation Administration said. The F.A.A. said air traffic controllers had been unable to communicate with the plane, which left from St. Louis Regional Airport in East Alton, Ill. around 3:30 p.m., for more than one hour.

Around 4:50 p.m., the Florida Air National Guard sent two F-15’s from the Homestead Air Reserve Base to investigate the unresponsive plane, which was not on its designated flight path, said Maj. Mark R. Lazane, a spokesman for the North American Aerospace Defense Command, also known as Norad.

The fighter jets approached the Cessna, after which the Cessna began “rapidly descending and subsequently crashed” into the Atlantic Ocean around 6 p.m.