Methane emissions from major oil sands facilities in the Athabasca Oil Sands Region (AOSR) of Alberta were measured in the summer of 2013 using two related aircraft mass-balance approaches. Tailings ponds and fugitive emissions of methane from open pit mines were found to be the major sources of methane in the region. Total methane emissions in the AOSR were measured to be ~ 20 tonnes of CH₄ per hour, which is 48 % higher than the Canadian Greenhouse Gas Reporting Program Emissions Inventory.