Its environmental efficiency has improved, with fuel burn per hundred passenger kilometres falling to 3.4 l/100km in 2017, down from 4.4l/100km in 2005.
However, it did produce more than 900 million tonnes of CO2 in 2018 and there is increasing pressure to decarbonise.
Read about what is being done (and what might be done in the future), including the use of market-based measures, such as the EU Emissions Trading System (EU-ETS) and how air traffic management can play its part.