Better food = less food waste. I see a lot of boxes not being emptied. So make sure it's good quality food to most peoples liking. Keep it simple and good

Use modern IT to implement dynamic codesharing, providing an interline journey following an optimized flight plan, rather than a static agreement.

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

Pay for luggage by weight.

If biofuel could be bought/added with points, people could spend their "soon-to-be-expired" points on biofuel rather than something unsustainable.

In a week/ some days before a flight, do sell “stand by tickets”, to a cost of approx. Euro 50 in Europa, Euro 200 intercontinental, , to increase the cabin factor.