Do not introduce Business class on intra-european flights. Plus is fair enough and very valuable for short flights and have a human price (like Norwegian and Ryanair).

For flights with a lot of empty seats, open more award seats short time before departure.

Introduce a "minimal comfort" seating class with basic amenities and reduced seat recline, allowing more passengers per flight and lowering per-person emissions.

Stop tankering on flights, lighter aircraft less fuel burnt and on shorter flights possibility to save deicing.

Tell the story on-board in the IFE to attract more companies that want to get involved and contribute!

Invite all travellers to bring their own coffee cup.