South Korea’s most recent fighter acquisition program gave the air force the type that it wanted, the Lockheed Martin F-35A Lightning, but not in the numbers it wanted. The budget stretched only to 40 fighters, not 60, and ever since the air force has hankered for the other 20. But those 20 additional aircraft may be F-35Bs instead, according to an industry source who says the air force is working toward the acquisition.