Something the EU could trivially implement - but rather than taxing the fuel directly, tax the fuel

Countries like the U.K. already charge poor tax on airlines - fly 20 people from london to paris in a 747 and you pay far less tax than than flying 100 people on an a319, despite causing far more pollution.

Instead charge based on the length of flight the the efficiency of the plane, regardless of how many people are actually on.

You’ll probably have to cap the tax on longer flights east otherwise everyone would transfer via Istanbul or ME3, but it wouldn’t require taxing fuel, or having airlines fuel up at the other end