Use powder soap instead of liquid soap in all lavatories, powder soap is much lighter thus reducing wieght.

Fill up empty seats by selling affordable return trips to unknown/secret destinations. Pick the destinations among those that have low occupancy close to departure time.

Implement the potential to offset carbon footprint by CDR technologies like enhanced rock weathering;

a better airline trolley for sorting garbage. Maybe with possibility for travellers to put in from the sides.

In M class on Intercontinental flights reduce the usage of plastics, ask the passenger to keep their glass for the entire flight before collecting it for recycling.

Instead of serving main meals on the flight briefly after takeoff, service the meal in the boarding area. Save load, effort and waste.