A bus is loaded onto an U.S. Air Force C-17 Globemaster III aircraft at Bagram Airfield, Afghanistan, Sept. 21, 2015. USAF cargo aircraft have transported 31,500 short tons of cargo throughout Afghanistan this year (U.S. Air Force photo by Tech. Sgt. Joseph Swafford/Released)

A U.S. Army Mine-Resistant Ambush Protected vehicle is offloaded from an Air Force C-17 Globemaster III aircraft at Bagram Airfield, Afghanistan, Sept. 21, 2015. USAF cargo aircraft have transported 31,500 short tons of cargo throughout Afghanistan this year (U.S. Air Force photo by Tech. Sgt. Joseph Swafford/Released)

A U.S. Army Mine-Resistant Ambush Protected vehicle is offloaded from an Air Force C-17 Globemaster III aircraft at Bagram Airfield, Afghanistan, Sept. 21, 2015. USAF cargo aircraft have transported 31,500 short tons of cargo throughout Afghanistan this year (U.S. Air Force photo by Tech. Sgt. Joseph Swafford/Released)

U.S. Soldiers assigned to the 1st Armored Division Resolute Support Sustainment Brigade walk to an Air Force C-17 Globemaster III aircraft to unload Mine-Resistant Ambush Protected vehicle at Bagram Airfield, Afghanistan, Sept. 21, 2015. USAF cargo aircraft have transported 31,500 short tons of cargo throughout Afghanistan this year (U.S. Air Force photo by Tech. Sgt. Joseph Swafford/Released)

A U.S. Army Mine-Resistant Ambush Protected vehicle is offloaded from an Air Force C-17 Globemaster III aircraft at Bagram Airfield, Afghanistan, Sept. 21, 2015. USAF cargo aircraft have transported 31,500 short tons of cargo throughout Afghanistan this year (U.S. Air Force photo by Tech. Sgt. Joseph Swafford/Released)

U.S. Army Mine-Resistant Ambush Protected vehicles are offloaded from an Air Force C-17 Globemaster III aircraft at Bagram Airfield, Afghanistan, Sept. 21, 2015. USAF cargo aircraft have transported 31,500 short tons of cargo throughout Afghanistan this year (U.S. Air Force photo by Tech. Sgt. Joseph Swafford/Released)