The son of Charles and Katharine (Lumsden) Cummings, Lumsden Cummings entered the Royal Flying Corps in October 1915. After completing flight training in the summer of 1917, he was posted to 1 Squadron in August. By the end of November, he scored five victories flying the Nieuport 27. On 9 February 1918, Cummings was in hospital. On leave at home in Canada, he was married on 16 October 1918 before returning to the U.K. a month later. With the war over, he left the Royal Air Force and returned to Canada on 5 March 1919. He became a civil engineer and lived in Toronto until his death in 1955.