By the mid-1980s, Flying Tigers operated scheduled cargo service to six continents and served 58 countries. It surpassed Pan American World Airways in 1980 as the world's largest air cargo carrier after acquiring its rival cargo airline Seaboard World Airlines on 1 October 1980. It also operated military contract services, most notably DC-8 routes between Travis Air Force Base, California and Japan in the 1970s, followed by weekly 747 passenger service between Clark Air Base, Philippines, and St. Louis, Missouri via Japan, Alaska, and Los Angeles during the 1980s. Covert flights for the military were not uncommon throughout the airline's history, given its roots in Civil Air Transport (CAT), as with its sister airline Air America, originally owned by General Claire Lee Chennault, commander of the Flying Tigers fighter squadron in Southeast Asia.