Deloitte is warning that the European Union’s plan to make air travel more eco-friendly could end up hurting European airlines and shifting passengers to foreign competitors.

Under the EU’s ReFuelEU policy, airlines are required to use more sustainable aviation fuel (SAF) to cut carbon emissions. But according to Deloitte’s new report, this could lead to higher ticket prices—up to 15% more on major routes like those between Europe and Asia by 2030.

That kind of cost difference might push travelers to fly with non-European carriers or choose connecting flights through airports like Istanbul or Dubai, where these fuel rules don’t apply. Some tourists may even skip EU destinations altogether to avoid extra costs.

This could mean lost business for EU airlines and airports, while also undermining the EU’s environmental goals by simply shifting emissions elsewhere instead of reducing them.

To avoid this, Deloitte is proposing a new system called “SAF Book and Claim,” where passengers can support the use of clean fuel without having to fly on SAF-powered planes directly. This would help balance the market and keep prices stable. The money raised from this system could go into funding more sustainable projects in aviation.

Deloitte also dismissed the idea of applying the EU’s carbon border tax (CBAM) to air travel, saying it wouldn’t work well under current laws and global agreements. Instead, they’re calling for a custom-built solution that works specifically for international flights.