An air traffic controller is being investigated after he jokingly told a pilot that he couldn't land and the pilot wound up circling the busy airport for an hour and a half.

Delta Flight 630 was coming in for a landing at Hartsfield-Jackson Atlanta International Airport, but an air traffic controller reportedly told the pilot that he couldn't land the plane. The controller was joking, but it was no laughing matter, the Daily Mail reports.

A few moments after denying him the landing, the controller said "I'm kidding, Delta 630. After you land I've got no one behind you. Expect to exit right. Delta 630 you're clear to land on (runway) 27-Left."

However it was too late. According to 11Alive Atlanta, the pilot had already changed course and ascended 40,000 feet because he thought he couldn't land. The Federal Aviation Administration is now investigating the incident. The agency found that the plane had reached as low as 1,000 feet before to ascended back to 40,000 feet.

The air traffic controller had tried to fix the incident by telling the pilot that he was kidding, but it was too late. The pilot said, "You sent us around. Delta 630 is on the go."

After ascending, the plane had to circle the airport for an hour an a half until the situation on the ground was cleared up and the plane was able to land safely.

According to the FAA, the pilot and passengers were never in danger. The FAA released a statement saying, "The FAA is investigating air traffic communications with Delta 630, a Boeing 777 aircraft on approach to Hartsfield-Jackson Atlanta International Airport."

It is not clear what kind of punishment the air traffic controller may receive.

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