An unidentified person called Southwest Airlines' corporate office Monday to say there was a device onboard a plane.
Flight 466 was sitting at gate D3 at Philadelphia International Airport on Monday afternoon when the call came in, TSA officials said.
All 59 passengers and crew were evacuated, and the plane was moved away from the terminal, officials said.
About 50 pieces of luggage were also searched.
Investigators said no device was found. They quickly gave the all-clear to let the plane fly. The flight was delayed about an hour.
The FBI and TSA are continuing to investigate the incident.