Keep your good clients - minimum 10 years as gold member gives you gold for life. Not necessarily 10 years in a row. Now 18 years with 1 missing in the middle = no go

Free coffee only for those who have reusable cups with them. Fee for paper cup or no paper cups at all.

Almost all passengers have their own phones/pads these days. Keep them connected with *good* wifi and IFE wont be needed, massive weight savings.

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

Getting more passengers on a bigger modern planes on certain routes will lower the emitted carbon dioxide per passenger as well as optimize the use of flight crews.

Add green flights on some departures. nothing is served on these flights, only hand luggage is allowed, but you earn more Eurobonus points if you choose such a departure.