Source: Airlines for America.
World Air Travel and World Air Freight Carried, 1950-2014
Air transportation has experienced a high growth rate since the 1970s, with air freight growing at a rate similar to that of passengers. The growth of air traffic has also been characterized by several setbacks linked with recessions (1973-1975; 1980-1984; 1990-1991; Asian Crisis of 1997; 2008-2009) or geopolitical instability (Gulf War of 1991; September 11 2001). In spite of these setbacks, the growth appears to be exponential and will level off when developing economies such as China, India and Brazil will become mature markets. When this takes place the global demand for air transportation is likely to peak.
The main factors behind the growth of passengers and freight traffic, as measured in passengers-km or tons-km, are linked with greater volumes being carried, but also the average distance over which passengers and freight are being carried. The changing structure of air transport networks is also at play since the development of hubs involves less direct connections and therefore longer distances being flown. The development of passenger services tends to induce freight demand since each additional plane usually offers additional cargo capacity, which can be made available on the market.