If you heard a loud noise in Flagstaff Monday night, you weren’t alone. Many people contacted us, wondering what the noise was. City of Flagstaff officials say large C-17 aircraft from the east coast practiced high-altitude landings at the Flagstaff Airport. Officials say because of Flagstaff’s altitude and airport in general, it makes the perfect place for C-17 pilots to go through that part of their training. The aircraft got out to a late start from their base and arrived in Flagstaff after 10 p.m. The practice is a common occurrence, so the next time you hear a loud noise and you live close to the airport, it’s probably one of the Air Force’s largest aircraft training in Flagstaff.