By December 1918, Holt Thomas claimed in an advertisement that Airco was the largest aircraft company in the world, being engaged in the construction of aeroplanes, engines and propellers in large numbers, as well as a number of airships and flying boats. The engines being built included licensed production of Gnome and Le Rhone rotary engines. The company's works at Hendon employed between 7,000 and 8,000 people and had the latest metal-working machinery, in addition to extensive testing equipment, including a materials testing laboratory and a wind tunnel. At one stage, Airco was reportedly completing one new aircraft every 45 minutes on average. During 1920, the aviation periodical Flight Magazine reported that, during the period from August 1914 to November 1918, the D.H. Airco aircraft manufactured in both Britain and the United States had comprised approximately 30 per cent of the total output of aeroplanes of these two allies.