American troops/USA Air Force

Airman Destri Snow, a 51st Security Forces Squadron defender, fires an MK-19 grenade launcher during weapons qualification training at Camp Rodriguez, South Korea, May 24, 2017. The training ensures defenders are vigilant and mission ready. (U.S. Air Force photo/Airman 1st Class Gwendalyn Smith)

An A-10 Thunderbolt II from the 442nd Fighter Wing, out of Whiteman Air Force Base, Mo., flies over the Atlantic Ocean during the National Salute to America’s Heroes Air and Sea Show media day May 26, 2017, at Miami Beach, Fla. Top tier U.S. military assets assembled in Miami during Memorial Day weekend to showcase air superiority while honoring those who have made the ultimate sacrifice. The 442nd FW teamed up with two HH-60G Pave Hawks and an HC-130P/N Combat King aircraft from the 920th Rescue Wing and the 129th Rescue Wing to headline the airshow by demonstrating combat search and rescue capabilities. (U.S. Air Force photo/Staff Sgt. Jared Trimarchi)

SpaceX's Falcon 9 rocket CRS-16 lifts off from Space Launch Complex 40 Dec. 5, 2018, at Cape Canaveral Air Station, Fla. The CRS-16, a cargo resupply mission to the International Space Station, carried more than 5,600 pounds of supplies to the ISS, including 250 research and science projects. (U.S. Air Force photo by Airman 1st Class Zoe Thacker)

A C-17 Globemaster III, from Joint Base Lewis-McChord, Wash., releases flares above the Selah Airstrip over Yakima Training Center, Nov. 15, 2018. The aircraft-dispensed flares are used as infrared countermeasures designed to defeat heat-seeking, surface-to-air or air-to-air missiles. (U.S. Air Force photo by Senior Airman Tryphena Mayhugh)

A Hawaii Air National Guard F-22 Raptor approaches a Wisconsin ANG KC-135 Stratotanker to receive aerial refueling, Dec. 11, 2018, over the Pacific Ocean, near the Hawaiian Islands. Sentry Aloha provides tailored, cost effective and realistic combat training for U.S. Air Force, ANG and other Department of Defense services to provide warfighters with the skill sets necessary to perform their homeland defense and overseas combat missions. (U.S. Air National Guard photo by Senior Airman John Linzmeier)

Air Force fire trucks ceremoniously spray a C-130H3 Hercules to land at the 165th Airlift Wing in Savannah, Ga., Dec. 17, 2018, during Maj. Gen. Jesse Simmons final flight. Simmons and members of the Georgia Air National Guard were returning home after supporting the 50th Anniversary of the Argentine Air Force. The Georgia ANG established a state partnership with Argentina in 2016. (U.S. Air National Guard photo by Tech. Sgt. Amber Williams)

Airmen assigned to the 451st Air Expeditionary Group work on loading munitions into the A-10 Warthog, Dec. 17, 2018, at Kandahar Airfield, Afghanistan. These Airmen are responsible for inspecting and loading munitions onto aircraft before they fly. (U.S. Air Force photo by Senior Airman Rito Smith)

Personnel from the 45th Operations Group, Detachment 3, simulate astronaut rescue and recovery operations, Dec 12, 2018, off the coast of Cape Canaveral Air Station, Fla. As the U.S. prepares to return to human spaceflight, Det. 3 in coordination with NASA and commercial partners, will play a direct role in rescue and recovery of astronauts because they are the only Department of Defense unit responsible for all aspects of human spaceflight recovery including planning of rescue tactics, real-world execution, and overall command and control of the human spaceflight mission. (U.S. Air Force photo by Airman 1st Class Dalton Williams)