Complex sentence: Located at Scott Air Force Base in Illinois about 20 miles from St. Louis, Missouri, JOSAC schedules aircraft from all four services (US Army, US Air Force, US Marine Corps, US Navy) to meet airlift requests from DoD officials.
Split into simpler sentences: Located at Scott Air Force Base in Illinois about 20 miles from St.Louis, Missouri. JOSAC (Joint Operational Support Airlift Center) schedules aircraft from all four services (USA, USAF, USMC, USN) to meet airlift requests from DoD officials.