South Korea, the US and Japan were set to conduct a joint air military exercise near the Korean peninsula on Sunday, weeks after the three countries carried out their first three-nation naval interdiction drills in seven years.

Sunday’s drill was set to include a formation flight in which the three nations’ fighter planes escort a US Air Force B-52H Stratofortress, Yonhap reported, citing unidentified US and South Korean military sources. While there have been cases of US-Korea and Japan-Korea joint drills, this would be the first time the three countries came together to conduct an aerial exercise, the report said.

The Stratofortress is a long-range, nuclear and conventional heavy bomber that can perform a variety of missions.

The joint training comes two weeks after a joint naval interdiction drill took place in international waters south of Korea.

That exercise, which simulated intercepting smuggling vessels, came after Washington accused the North of making illicit weapons shipments to Russia. The two-day exercise involved the USS Ronald Reagan aircraft carrier group, an Aegis-equipped destroyer from South Korea and a destroyer from Japan. In response, North Korea warned it’s ready to use its most powerful weapons in a strike.

North Korea last fired two short-range ballistic missiles just ahead of a summit between leader Kim Jong Un and Russian President Vladimir Putin on Sept. 13 at the Vostochny Cosmodrome space center in the Amur region.