BEJA AIR BASE, Portugal - An F-16 fighter aircraft performs a 'stop-and-go' at Beja Air Base, Portugal Oct. 21, 2015 in support of Exercise Trident Juncture 2015. More than 30,000 troops from more than 30 NATO and allied nations are participating in the exercise. Trident Juncture is an annual NATO Response Force certification exercise. (U.S. Air Force photo by Airman 1st Class Luke Kitterman/Released)