A bomb threat on a Philadelphia-bound plane was one of five called in to the Transportation Security Administration on Tuesday, police said.
An American Airlines Flight 648 from San Diego to Philadelphia was diverted to a remote part of the airport, evacuated and searched Tuesday morning, said Chief Inspector Joseph Sullivan.
Sullivan said the bomb threats were not considered credible, because the sheer number of them would seem to indicate an incredibly high degree of coordination.
The plane was searched however, out of an abundance of caution.
NBC News reports that the four other flights were a Korean Air flight from Seoul to San Francisco, a Delta flight from Los Angeles to Atlanta, a United flight from San Francisco to Chicago and a Volare flight from Portland, Oregon to Guadalajara, Mexico.
Police in Philadelphia used explosives-detecting dogs to search the plane and luggage.
American Airlines said in a statement that the passengers were accommodated with customer service and assisted with new bookings to their final destination.