An F-16 Fighting Falcon aircraft is "hot refueled" on Ramstein Air Base, Germany, Oct. 4, 2018. A hot refuel is conducted while the engines of an aircraft are still running. The 435th Air Ground Operations Wing led Temperate Ace, a proof-of-concept exercise demonstrating strike force capabilities. (U.S. Air Force Photo by Airman 1st Class Noah D. Coger)