The non-CO2 effects of aviation have been acknowledged by scientists but ignored by policymakers. It is estimated that gases other than CO2 have at least as large a climate impact as CO2. The European Commission has so far failed to address aviation’s non-CO2 effects despite undertaking to do so in 2008. This risks undermining the EU’s climate policy. This report's authors, CE Delft, recommend that the Commission acts on its 2008 promise and proposes measures such as a charge on NOx emissions and earmarks funds for research into other non-CO2 effects such as contrail and cirrus formation and their avoidance.