This collection contains considerable material relating to aviation history, particularly in western and northern Canada, including material on: the Keng Wah Aviation School for Nationalist Chinese pilots; the RCAF; illustrations of the technology of flight; reference material; and microfilms of the Hudson Strait Expedition fonds (1927-1928) and "The Bulletin" (Western Canada Airways, 1929-1937). Additionally, there is material on Tweddell's other research interests, notably aerial mapping and surveying.