The 91st Aero Squadron was a unit of the Air Service, United States Army that fought on the Western Front during World War I. The 91st was one of the first five American flying squadrons to reach France, arriving at Chaumont Hill 402 Aerodrome on 15 November 1917. The current United States Air Force unit which holds its lineage and history is the 91st Cyberspace Operations Squadron, assigned to the 67th Cyberspace Wing, Kelly Field Annex, Lackland Air Force Base, Texas.