sentences:  Troops, Panama Canal Zone, and beginning on 1 July 1917, Army aviation units were assigned directly to the Panama Canal Department, which was the senior United States Army headquarters in the Canal Zone.During World War I, the 7th Aero was assigned to patrol for German U-Boats offshore of the Canal Zone under direction of Coast Defenses of Cristobal, from 1 June – 15 November 1918.The 7th Aero Squadron was assigned to several fields during 1917 and 1918, those being Corozal (16 April); Empire (May); Fort Sherman (29 August); Cristobal (March 1918) before finding a permanent home at Coco Walk, which became France Field in May 1918.