Owing to the strong sector growth, the comparatively limited number of mitigation options and the long fleet turnover times, achieving zero-carbon emissions is particularly challenging for aviation. The EPSRC-funded “Towards Zero-Carbon Aviation” (TOZCA) project develops a comprehensive tool suite to simulate the most cost-effective transition towards a net zero-carbon aviation system by 2050 through changes in technology, fuels, operations, consumer behaviour and use of competing modes.  TOZCA, which is led by the UCL ATSlab, is a collaborative effort with the University of Leeds, the University of Southampton, and the Massachusetts Institute of Technology.  TOZCA also collaborates with around 20 stakeholders from industry, government, thinktanks and NGOs.