The U.S. and South Korean air forces kicked off an annual series of joint air exercises on Monday, which will be held less frequently this year in a move that some are interpreting as an attempt to avoid provoking North Korea.

The five-day Ssangmae Training, or Buddy Squadron exercise, is taking place at Osan Air Base, roughly 30 miles south of the capital city, Seoul’s Defense Ministry said in a press release.

The battalion-level air exercises held throughout the year began in 1991 to allow ROK and U.S. pilots “to practice the latest tactics, systems and procedures together and to