Source: Airlines for America. IATA.
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; the Financial Crisis of 2008-2009), geopolitical instability (Gulf War of 1991; September 11, 2001) and even the COVID-19 pandemic (2020-21). The latter represents the most significant singular event impacting the airline industry, notably the passenger segment that experienced a drop of 65% in 2020. Despite these setbacks, growth appears to be continuous and will level off when developing economies like China, India, and Brazil 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 and 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 average distances being flown between airport pairs. The development of passenger services tends to induce freight supply since each additional plane usually offers additional cargo capacity, which can be made available on the market. This additional capacity can incite new cargo demands.