MINOT AIR FORCE BASE, N.D. -- Firefighters with the 5th Civil Engineer Squadron climb stairs at Minot Air Force Base, North Dakota, Sept. 11, 2018. The fire department held a memorial stair climb in honor of those who gave the ultimate sacrifice responding to the 9/11 attacks. Volunteers climbed 110 flights to symbolize the height of the twin towers. (U.S. Air Force photos by Senior Airman Alyssa M. Akers)