The Sports and Fitness Expo Friday was well attended as people arrived to pick up their racing bibs at the Nutter Ctr.. The Greene County Convention & Visitors Bureau estimates that the economic impact of this weekend’s Air Force Marathon festivities to the region will be $12.7 million, with Fairborn and Beavercreek the two cities that benefit the most.More than 30,000 runners and supporters from all 50 states and 20 countries are in town this weekend for the Air Force Marathon, which starts and ends at the National Museum of the United States Air Force. An after-party is scheduled saturday at The Greene, capping off a three-day event that also included the Sports and Fitness Expo Thursday and Friday at the Nutter Center, a 5K race Friday night, and a half marathon and 10K saturday.“A $12.7 million impact in three days is a significant piece of business with us, ” said Allen Stebelton, sales manager for the GCCVB.