Thailand's military government on Tuesday approved the purchase of eight supersonic T-50TH trainer jets from South Korea at a cost of 8.8 billion baht ($258 million).

Prime Minister Prayuth Chan-ocha said after the Cabinet approved the purchase that it is the second stage of a 16-plane acquisition that was planned in 2015, when a deal for the first four was made. Those four are to be delivered next year.

The South Korean planes will replace Czech-made L-39 trainers, which Prayuth said have been in service for more than two decades

The contract for the new planes is expected to be signed by the end of the month with Korea Aerospace Industries Ltd., which designed and developed the aircraft with U.S. aerospace company Lockheed Martin.