Despite a clear blue sky, Liberty County residents heard “thunder” Thursday and Friday. Those who looked skyward found the source of the thunder was a C-17 Globemaster landing and taking off from Wright Army Airfield.The two-day exercise was conducted by the Air Force Reserve’s 315th Air Mobility Command, which is based in Charleston, and the South Carolina Army National Guard’s 1st Battalion 118th Infantry Regiment, which is based at McEntire Joint National Guard Base in Columbia. Bill Phipps, manager of Wright AAF/Midcoast Regional Airport, said the successful exercise debunks the myth that Wright’s 5,000-foot runway isn’t long enough for large planes.“Our runway is just over 5,000 feet long,” Phipps said.