South Korea will benefit from economies of scale when production of the F-35 stealth jet goes into full swing in the next five years if it signs a contract for 40 aircraft for delivery starting from 2018, a senior Lockheed Martin official said. Seoul is set to confirm a plan to buy 40 F-35As through the U.S. foreign military sales (FMS) program without open bidding, while the Defense Acquisition Program Administration (DAPA) and the finance ministry are currently deliberating the total budget.