The pilot and passenger were the only ones on board the 12-seat Cessna Caravan that took off from the Bahamas.
In audio obtained by ABC News, the passenger can be heard telling Air Traffic Control he's got "a serious situation."
"My pilot has gone incoherent. I have no idea how to fly the airplane," he said.
In another audio clip, Air Traffic Control asks the passenger where he was located.
"I have no idea," the passenger responded. "I see the coast of Florida in front of me and I have no idea."
Sources told ABC News the controller involved is a certified flight instructor with experience working with Cessna aircraft.
"No problem, just continue to stay wings level, maintain 5,000 and follow the coast and we'll try to find you here on the radar," the controller said.
Air Traffic Control located the plane on its radar flying just off the coast of Boca Raton.
The passenger miraculously ended up landing the airplane at the airport safely.
"The person on the airplane who had no aeronautical experience listened very carefully and obviously followed instructions with great calm," said aviation expert John Nance. "That's what made the difference."
The pilot was taken to the hospital.
The Federal Aviation Administration is investigating the incident.