This is a partial list of original Air Service, United States Army "Aero Squadrons" before and during World War I. Units formed after 1 January 1919 are not listed.

Aero Squadrons were the designation of the first United States Army aviation units until the end of World War I. These units consisted of combat flying, training, ground support, construction and other components of the Air Service. After World War I ended, the majority of these squadrons were demobilized. Some however were retained during the interwar period of the 1920s and 1930s, and served in all theaters of operation during World War II. Today, the oldest squadrons in the United States Air Force and Air National Guard can trace their lineage back to the original Aero Squadrons of World War I.

Overview

In January 1918 a new numbering scheme for aero squadrons was set up. Numbers 1–399 would be for Aero Service Squadrons (AS). 400–599 Aero Construction Squadrons (ACS), 600–799 Aero Supply Squadrons and 800–1099 Aero Repair Squadrons. Non-notable support squadrons are not listed.

The numerical designation of school squadrons at the various flying fields in the United States was discontinued in July 1918, and replaced by letter designation. For example, the 2d Aero Squadron became Squadron A, Kelly Field. In November 1918, the personnel of the lettered squadrons of each flying field was merged into a single Flying School Detachment at such station.

 Formed prior to 2 April 1917 American Expeditionary Force combat squadron Planned American Expeditionary Force combat squadron (never entered combat) Currently active as United States Air Force/Air National Guard squadron

In addition to the Aero Squadrons, whose mission supported airplanes in one way or another, Air Service Spruce Squadrons have been noted and listed. A part of the Signal Corps, they were located in Oregon and Washington states. When the U.S. entered World War I, it was quickly discovered that the nation had no capacity to build warplanes in quantity. Spruce timber, vital to wing construction was in critically short supply. In 1918 the United States Army stepped in and took over the production of airplane spruce in the pacific northwest, with the Spruce Production Division organizing loggers and constructing a plant to process the wood, construct roads and railroads into the forests to access and cut the timber.

Men in the Spruce Squadrons were part of the Signal Corps along with the Aero Squadrons, as the Signal Corps oversaw all Army aviation. About 50,000 soldiers were assigned to Spruce Squadrons, overseeing about 100,000 lumber workers, were assigned to small camps in the Pacific Northwest. Many of these men were itching to go "over there" and take part in combat, however, their labor and skills to produce spruce lumber were needed far more, in the forests of the Pacific Northwest to produce the materiel needed to build aircraft. The camps where the soldiers were located are listed on the individual squadron entry.

Squadrons

1st to 24th Aero Squadrons At the time of the United States entry into World War I in April 1917, three Aero Squadrons had been formed. The 1st and 3d were in the United States, and the 2d was in the Philippines. The 6th, being destined for Hawaii and the 7th, destined for the Panama Canal Zone were organizing. The 4th and 5th, to be based in the continental United States had yet to receive personnel.

Aero Squadron Established World War I Notes/Subsequent History 1st Aero Squadron 5 March 1913 Formed as: 1st Provisional Aero SquadronPre-WWI service in Mexico and TexasAEF: 6 April 1918 – 12 May 1919Corps Observation SquadronCombat with I Corps Observation GroupUnited States War Department (1920), Battle Participation of Organizations of the American Expeditionary Forces in France, Belgium and Italy, 1917–1919, Washington, Government Printing Office, 1920 Patrols in the Toul, Aisne-Marne, Vesle and Toul-Verdun Sectors St. Mihiel Offensive Campaign Aisne-Marne Defensive Campaign Meuse-Argonne Offensive Campaign Most senior organization in the United States Air Force Returned to the United States in August 1919, stationed at Park Field, Tennessee Redesignated in the Army Air Service as the 1st Squadron (Observation) on 14 March 1921; Re-designated as the 1st Observation Squadron on 15 November 1922; Reorganized and re-designated 1st Bombardment Squadron on 1 March 1935. Currently: 1st Reconnaissance Squadron, Beale AFB, California 2d Aero Squadron 1 December 1915 Formed as: 1st Company, 2d Aero SquadronPre-WWI service in the PhilippinesInstructional flying squadronRe-designated: Squadron A, Kelly Field, Texas, July 1918Demobilized: 18 November 1918 Constituted in the Air Service, United States Army on 3 June 1919, at Rockwell Field, California, as the 2d Aero Squadron; Transferred on 24 December 1919, to the Philippines assigned to the Philippine Department. Redesignated in the Army Air Service as the 2d Squadron (Observation) on 14 March 1921; Consolidated on 8 April 1924, with the 2d Aero Squadron; Re-designated as: 2d Observation Squadron on 25 January 1923 Stationed at Nichols Field, Philippines on 7 December 1941, subsequently wiped out in the 1941–1942 Battle of the Philippines; Inactivated 2 April 1946; Re-activated 1 January 1949. Currently: 2d Air Refueling Squadron, McGuire AFB, New JerseyMaurer, Maurer. Combat Squadrons of the Air Force: World War II. Maxwell Air Force Base, Alabama: Office of Air Force History, 1982. 3d Aero Squadron 1 November 1916 Pre-WWI service in TexasInstructional flying squadronRe-designated: Squadron A, Post Field, Oklahoma, July 1918Demobilized: 2 January 1919 Constituted in the Air Service, United States Army on 13 May 1919, at Mitchel Field, New York, as the 3d Aero Squadron; Transferred on 5 July 1919, to the Philippines assigned to the Philippine Department. Redesignated in the Army Air Service as the 3d Squadron (Pursuit) on 14 March 1921; Re-designated as the 3rd Pursuit Squadron on 25 January 1923Consolidated on 8 April 1924, with the 3rd Aero Squadron Stationed at Clark Field, Philippines on 7 December 1941, subsequently wiped out in the 1941–1942 Battle of the Philippines; Inactivated 2 April 1946. Re-designated 3d Tactical Fighter Squadron on 12 March 1973; Activated on 15 March 1973. Currently: 3d Flying Training Squadron, Vance AFB, Oklahoma 4th Aero Squadron 5 May 1917 Planning for organization began in December 1916 when the United States Army made plans for a force of seven air squadronsInstructional flying squadronRe-designated: Squadron B, Post Field, Oklahoma, July 1918Demobilized: 2 January 1919 Constituted in the Air Service, United States Army on 23 June 1919, at Hazelhurst Field, New York, as the 4th Aero Squadron; Transferred on 24 January 1920, to Luke Field, Hawaii assigned to the Hawaiian Department. Redesignated in the Army Air Service as the 4th Squadron (Observation) on 14 March 1921; Re-designated as the 4th Observation Squadron on 25 January 1923 Consolidated on 8 April 1924, with the 4th Aero Squadron; Reorganized and re-designated 4th Reconnaissance Squadron (Medium Range) on 25 January 1938 Assigned to Hickam Field, Hawaii on 7 December 1941, largely destroyed during the Pearl Harbor Attack; Re-designated 394th Bombardment Squadron (Heavy) on 22 April 1942 Currently: 394th Combat Training Squadron, Whiteman AFB, Missouri 5th Aero Squadron 5 May 1917 Planning for organization began in December 1916 when the United States Army made plans for a force of seven air squadronsInstructional flying squadronRe-designated: Squadron A, Souther Field, Georgia, July 1918Demobilized: 11 November 1918 Constituted in the Air Service, United States Army on 23 June 1919, at Hazelhurst Field, New York, as the 5th Aero Squadron; Transferred in November 1919 to Mitchel Field, New York Redesignated in the Army Air Service as the 5th Squadron (Observation) on 14 March 1921; Re-designated 5th Observation Squadron on 25 January 1923; Consolidated in April 1924 with the 5th Aero Squadron Currently: 5th Reconnaissance Squadron, Beale AFB, California 6th Aero Squadron 13 March 1917 Planning for organization began in December 1916 when the United States Army made plans for a force of seven air squadronsGarrisoned at: Luke Field, Ford Island, Hawaii Redesignated in the Army Air Service as the 6th Squadron (Pursuit) on 14 March 1921; Re-designated as the 6th Pursuit Squadron on 25 January 1923; Re-designated: 6th Pursuit Squadron on 25 January 1923 Re-designated: 6th Night Fighter Squadron on 17 January 1943; Inactivated on 20 February 1947 Currently: 6th Weapons Squadron, Nellis AFB, Nevada 7th Aero Squadron 29 March 1917 Planning for organization began in December 1916 when the United States Army made plans for a force of seven air squadronsGarrisoned in Panama Canal Zone Redesignated in the Army Air Service as the 7th Squadron (Observation) on 14 March 1921; Re-designated: 7th Observation Squadron on 25 January 1925. Re-designated: 397th Bombardment Squadron (Heavy) on 11 May 1942; Inactivated on 1 November 1946. Currently: 7th Reconnaissance Squadron, NAS Sigonella, Italy 8th Aero Squadron 21 June 1917 AEF: 8 December 1917 – 3 May 1919Corps Observation SquadronCombat with IV and VI Corps Observation Groups Patrols in the Toul Sector St. Mihiel Offensive Campaign Returned to the United States in June 1919 and assigned to Kelly Field, Texas; Re-designated 8th Surveillance Squadron; Transferred on 13 August 1919, less Flight B, to the U. S. Army Airdrome, McAllen, Texas. Redesignated in the Army Air Service as the 8th Squadron (Attack) on 14 March 1921; Entire squadron transferred 2 July 1921, to Kelly Field, Texas. Re-designated as the 8th Attack Squadron 25 March 1923; Reorganized and re-designated 8th Bombardment Squadron on 1 December 1939 Currently: 8th Special Operations Squadron, Hurlburt Field, Florida 9th Aero Squadron 14 June 1917 AEF: 28 October 1917 – 8 June 1919Night Observation SquadronCombat with First Army Observation Group Patrols in the Toul Sector St. Mihiel Offensive Campaign Meuse-Argonne Offensive Campaign Returned to the United States in June 1919 and assigned to March Field, California Redesignated in the Army Air Service as the 9th Squadron (Observation) on 14 March 1921; Inactivated on 29 June 1922, at March Field; Re-designated as the 9th Observation Squadron on 25 January 1923. Re-designated as the 9th Bombardment Squadron 24 March 1923; Organized by June 1929 in the Regular Army Reserve at Kelly Field, Texas. Activated on 1 April 1931, less Reserve personnel. Re-designated as the 9th Bombardment Squadron (Heavy) on 6 December 1939. Currently: 9th Bomb Squadron, Dyess AFB, Texas 10th Aero Squadron 31 May 1917 Organized at Kelly Field, TexasTransferred to Chanute Field, Illinois, 7 July 1917 (First assigned unit to Chanute Field)AEF: 26 December 1917 – May 1919 Service Support Squadron3d Aviation Instruction CenterIssoudun Aerodrome erroneously demobilized: Jun 1919 at Mitchell Field, New York; re-constituted at Bolling Field, D.C., Jul 1919; final demobilization 31 December 1919.Gorrell's History of the American Expeditionary Forces Air Service, 1917–1919, Volume 2, 9th and 10th Aero Squadrons 11th Aero Squadron 26 June 1917 AEF: 1 January 1918 – 1 May 1919Day Bombardment SquadronCombat with 1st Day Bombardment Group Patrols in the Toul Sector St. Mihiel Offensive Campaign Meuse-Argonne Offensive Campaign Returned to the United States in June 1919, assigned to Fort Bliss, Texas; Participated in the Mexican Border Patrol August–November 1919