A child was apparently allowed to direct aircraft from the control tower of New York's JFK, one of the world's busiest airports.
Two controllers have been suspended while the Federal Aviation Authority investigates the incident which took place during a week-long school break.
The investigation began after tapes of the child's conversation were posted on the internet.
The voice can be heard making five transmissions to pilots preparing for take off on February 17.
In one exchange, the child can be heard saying, "JetBlue 171 contact departure."
The pilot responds: "Over to departure JetBlue 171, awesome job."
A male voice in the tower then says: "That's what you get, guys, when the kids are out of school."
The child later clears another plane for take off, and says, "Adios, amigo."
The FAA said : "Pending the outcome of our investigation, the employees involved in this incident are not controlling air traffic."
It added: "This behaviour is not acceptable."