The Shahjalal International Airport originated in 1941, during the second world war, as the British government built a landing strip at Kurmitola, several kilometres north of Tejgaon, as an extra landing strip for the Tejgaon Airport. At that time Tejgaon was a military airport, to operate warplanes towards the war fields of Kohima (Assam) and Burmese war theatres. Shah Amanat International Airport was a combat airfield as well as a supply point and photographic reconnaissance base by the United States Army Air Forces Tenth Air Force during the Burma Campaign 1944-1945. Known American units assigned to Chittagong were: 80th Fighter Group, flew P-38 Lightning fighters over Burma between March 1944 and February 1945; 8th Reconnaissance Group, between October and December 1944 (various detachments); and 4th Combat Cargo Group, flew C-46 Commando transports between January and June 1945. Osmani International Airport in Sylhet was built during British rule as Sylhet Civil Airport, partly to check Japanese aggression from Burma. Biman Bangladesh Airlines earns most of its revenue from this airport.