The airline industry contributes around 2.5% of global carbon emissions, but scientists believe it has a much higher impact on climate change than this figure suggests. 

While it is not a global regulator of the airline industry, ICAO is the UN body that promotes co-operation among member states on air transport. It cannot impose rules on countries, but national governments usually abide by what is agreed at ICAO meetings.

The air transport industry has been under increasing pressure from consumers and scientists to try to find ways to decarbonise air travel for several years, with limited success.

At the ICAO triennial assembly in Montreal, member states finally agreed to support a net zero target for 2050, despite grumbles from China and Russia.