Lt. Col John Caldwell, commander of the U.S. Air Force Air Demonstration Squadron Thunderbirds, Nellis Air Force Base, Nevada, waves after his aircraft receives fuel April 18, 2020, in the skies over Colorado. The Thunderbirds are the Air Force’s premier aerial demonstration team and performed flyovers for the Air Force Academy’s class of 2020 graduation as well as all frontline COVID-19 responders that have worked tirelessly to combat the coronavirus. (U.S. Air Force photo by Airman 1st Class Nilsa E. Garcia)