SEOUL (AFP) - A South Korean military trainer jet crashed on Monday during an exercise, killing both pilots on board, military authorities said. The British-made Hawk trainer aircraft crashed soon after taking off from its base in Yecheon about 240 kilometres (144 miles) southeast of Seoul, the defence ministry said. An investigation was under way into the cause of the accident, it said. The South Korean air force has 16 Hawks, made by the British defence giant BAE Systems, which were first introduced in 1992, Yonhap news agency said.