Countries already apply taxes to flights in or outbound from their territories. Airlines already apply "fuel surcharges" as part of their ticketing. Adding a,

Countries already apply taxes to flights in or outbound from their territories. Airlines already apply "fuel surcharges" as part of their ticketing. Adding a, for example, EU-wide tax on outbound flights based on the distance of origin/destination, would be one way of implementing. Getting international agreement on, for example, having it apply only to outbound flights, would mean that is not a tax on imports, that could be considered a tariff. The income could then be spent on subsidizing the other costs of decarbonization.