Engage travellers actively through the app: compete to save energy related to travel (pack light, public transport, direct flights) & display flight energy-consumption

Implement sharkskin technology or (my own) coating to reduce air resistance and micro-drag from the fuselage.

Adopt single-engine taxiing to save fuel during ground operations.

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!

Make visible in the app how many people are flying on green fuel on booked flights, to encourage other people to do.

Allow free rebooking on the day of departure to a shorter route or a route with less stops when available, even in low booking classes and without status.