Chief Warrant Officer Three Mark S. O'Steen was born on 6 October 1959 in Wytheville, Virginia. He was one of four crewmembers killed on 30 January 2003 when their MH-60L Black Hawk helicopter, #185, crashed near Bagram, Afghanistan while conducting aerial gunnery training in support of Operation ENDURING FREEDOM.

CW3 O’Steen volunteered for service in the Army in 1985 when he enlisted as a linguist. After five years of enlisted service, he was selected to attend the Warrant Officer Candidate Flight School at Fort Rucker, Alabama. Upon graduation in 1990, he was assigned to Yong San, Korea where he served for one year as a UH-60 Black Hawk pilot. His next assignment brought him to Fort Campbell, Kentucky, where he served for three years as a UH-60 Black Hawk pilot with 5th Battalion, 101st Airborne Division (Air Assault). He was then assigned for one year to Palmerola, Honduras, as a UH-60 Black Hawk pilot. He was next assigned to Fort Bragg, North Carolina, where he served for three years as a UH-60 Black Hawk Instructor Pilot. CW3 O’Steen was again assigned to Fort Campbell where he began his distinguished five year career as a Night Stalker in Delta Company, 1st Battalion, 160th Special Operations Aviation Regiment (Airborne). With the Hooter Brothers, he served as a MH-60L Black Hawk DAP and Assault Fully Mission Qualified Pilot, an Instructor Pilot, and a Standardization Instructor Pilot. CW3 O'Steen flew over 3,165 hours and 1,182 night vision goggle hours. He was a combat veteran of Operation ENDURING FREEDOM.

CW3 O'Steen was a graduate of the University of New York, Regents College with a Bachelor of Science Degree in Liberal Arts. His military schools include the Warrant Officer Aviation Advanced Course, Rotary Wing Instrument Flight Examiners Course, Instructor Pilot Course, Department of Defense High Risk Survival Course, and the Army Survival, Evasion, Resistance, and Escape (SERE) Course.

CW3 O’Steen’s awards and decorations include the Meritorious Service Medal, Army Commendation Medal (w/4 OLC), Army Achievement Medal (w/1 OLC), Joint Meritorious Unit Award, Army Good Conduct Medal, National Defense Service Medal (w/1 Bronze Service Star), Armed Forces Expeditionary Medal, Non-Commissioned Officer Professional Development Ribbon, Army Service Ribbon, Overseas Service Ribbon (2nd Award), Senior Aviator Badge, Parachutist Badge, and the Air Assault Badge. He was posthumously awarded the Legion of Merit, Bronze Star Medal, and the Air Medal.

CW3 O’Steen is survived by his wife, Amy; daughters, Brittany and Jana; son, Geoffrey; brothers, David, Patrick, and James and sister, Janice. He is laid to rest in Ozark, Alabama, at Woodlawn Memorial Gardens. The Special Operations Aviation Green Platoon Training Area at Fort Campbell, Kentucky, is dedicated in honor of the fallen crewmembers of Aircraft Tail #185.