The Air Force is planning another training session next month in the massive Powder River Training Complex over the Northern Plains. The Combat Raider exercise is scheduled for three days beginning Oct. 16. It will involve several different types of military aircraft. The 35,000-square-mile complex over the Dakotas, Montana and Wyoming is the largest over the continental U.S. It’s been in use for three years. Large-scale exercises are limited to 10 days per year.