The airline said the pilot on the Friday afternoon flight used the intercom to wish a happy birthday a woman on board who is the mother of an air traffic controller and several passengers became upset when the phrase "mom on board" was misunderstood as "bomb on board," the Long Island Press, Syosset, N.Y., reported Monday.
"The pilot made an announcement that was misunderstood," a Southwest spokeswoman said.
The Federal Aviation Administration said it was "not investigating the pilot or the flight crew" over the incident.
"Pilots and controllers will sometimes engage in brief greetings," the FAA said in a statement. "If such conversations go beyond this limit, controllers are counseled to refrain from such unnecessary talk."