Luke Airmen participate in 9/11 Tower Challenge Published Sept. 20, 2021 By Senior Airman David Busby 56 FW/PA Over 1,500 participants attended the 9/11 Tower Challenge at Gila River Arena, Glendale, Arizona including civilians, active-duty and reserve military personnel, veterans, firefighters and first responders. Participants walked up and down stadium stairs representing the 110 flights of stairs climbed by New York City firefighters during the attacks on the World Trade Center and in honor of those who lost their lives.