At least five flights were targeted by phoned-in bomb threats Tuesday,  June 2, government sources told NBC News. The threats weren’t considered credible.

Four of the five flights — among them one from San Diego to Philadelphia, one from Los Angeles to Atlanta and one from San Francisco to Chicago — landed safely Tuesday, while the other was still en route to San Francisco from Seoul, South Korea.

Korean Air Flight 23 from Seoul to San Francisco was still in the air and is scheduled to land Tuesday afternoon.

The flights that landed safely were US Airways Flight 648 from San Diego to Philadelphia, Delta FLight 55 from Los Angeles to Atlanta, United Flight 995 from San Francisco to Chicago and Volare Flight 939 from Portland, Oregon, to Guadelajara, Mexico.

At the Philadelphia airport, police with search dogs boarded the threatened US Airways flight, after a threat indicated there were multiple devices aboard Flight 648.

Airline spokeswoman Victoria Lupica says passengers were taken off the plane and transported to a terminal. They were reunited with their luggage and personal items and were free to go.