Find ways to allow tax-free purchases to be done in departing airport and to be picked up at the airport were I land. It could save a lot of weigh/fuel.

Reduce food waste by dropping vegan food that nobody eats

In Plus and Business on long haul - hand out amenity kits by request instead of placing them on all seats.

Dynamic seating - people with checked in baggage should be placed towards the rear of the plane as they are more likely to have to wait anyway on arrival at destination.

Earn EuroBonus points when recycling. Collaborate with apps such as Bower and Repeat in Sweden. They offer cash rewards for recycling. Why not reward points instead!

An incentive to make longer trips rather than shorter trips would make traveling with air more sustainable.