The flight over Irisuna, about 70km from the main Okinawa island, was part of the country's 11-day nationwide 05JX. The drills, which end Monday, also include an air defence exercise in Japan’s north and simulated attacks on five nuclear reactors including the Fukushima plant. Such military exercises are set to expand in scope and become more frequent after PM Fumio Kishida in December unveiled a military build-up that will double defence spending over the next five years to bolster Japan's Self Defence Forces against possible adversaries, including China.