Monitoring officials from the 128th Air Refueling Wing, Milwaukee, activate a canister of colored smoke, which indicates a simulated attack upon the military installation, during an Ability to Survive and Operate exercise at Gen. Mitchell International Airport on Saturday, May 14, 2011. The ATSO exercise tested the readiness and preparedness of Airmen to survive and operate during chemical, nuclear, and biological attacks. Furthermore, the exercise reflected the potential threats Airmen could encounter while deployed overseas.