Kenneth R. Sealy. The Geography of Air Transport. London: Hutchinson University Library, 1966. Revised edition. A bit outside my usual timeframe, but I had to rescue it from a secondhand bookshop. Lots of statistics and maps about world aviation in the early jet age, but also going back to the interwar period. If I ever need to know the seasonal variation of BEA traffic types in 1963-64, daily seat/miles for leading western European airlines in 1961, isopleth maps of contact flying hours for the British Isles (day and night), or indeed passenger numbers for the Scottish air ambulance service going back to 1934, I know where to look.