Applying World Resources Institute (WRI) estimates for carbon dioxide equivalent emissions (i.e. CO2 per airline passenger kilometre for flights over 1600 kilometres, 0.12kg per airline passenger kilometre for flights of between 500 and 1600 kilometres, and 0.15kg per airline passenger kilometre for flights of less than 500 kilometres, which includes CO2 plus other greenhouse gases from jet fuel combustion), total CO2 equivalent emissions from BHP Billiton air travel in the reporting period is estimated to be 61,240 tonnes.