Courtesy: British Government Public Information Films en.wikipedia.org www.heathrowairport.com The story of a great engineering feat – the building, at Heathrow, of one of the largest airports in the world.April 1944 Great Western Aerodrome started its transformation from a privately owned small grass airfield to Heathrow. One of the worlds busiest airports. Londons main civil airport replacing Croydon Airport. The airport opened fully for civilian use on 31 May 1946. London Heathrow International Airport’s one terminal was in fact an army surplus tent situated a short walk from the aircraft.