Over the past 20 years, the European Union (EU) has shifted the emphasis of its trade policy from multilateral agreements towards bilateral preferential trade agreements (PTAs) and, more recently, to unilateral policy instruments. In this article we analyze the EU’s growing ambitions in promoting environmental sustainability in the context of these shifts. We advance an analytical and a conceptual argument, focusing on a product group that is highly relevant to the EU’s green transition: aviation fuels. We argue that the increasing hardness and ambition of the EU’s environmental policy instruments on the sustainability of aviation fuels contributes to a trend of ‘unilateralization’ in EU trade policy. Our analysis further illustrates how the complementary qualities of hardness and ambition in the multi-, bi-, and unilateral EU instruments lead to their flexible combination in the EU trade policy mix. Based on these findings, we propose to describe and critically analyze the EU’s current approach as ‘flexilateralism’. The EU has changed from prioritizing multilateralism to a more pragmatic, flexilateral approach, rather than for fully fledged bilateralism or unilateralism. This is what the EU’s more assertive ‘strategic autonomy’ may be about: a flexilateral approach to better address issues such as environmental sustainability with the most useful combination of instruments available.