The airfield's runways were paved in 1939 in preparation for operations during World War II. RCAF Station Rockliffe participated in the British Commonwealth Air Training Plan and — as the nearest airport to the centre of the capital — was involved in many other kinds of testing, training, and transport operations, including the transport of mail to Europe using B-17 Flying Fortresses and B-24 Liberators. Immediately after the war, in September 1945, RCAF Station Rockcliffe was the site of the first jet aircraft demonstration in Canada.