Make the app as lightweight as possible. Remove images, animations and leave only the bare necessities. This saves data transfer and storage - which in turn saves energy.

If more people could eat the same food, there would be less food waste and more happy customers.

Ensure correct recycling of plastics by unwrapping meals and plastic protected crisp breads before handing to the customer.

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

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

Travel light = bring less than 8 kg. If you do so, you should be rewarded with points. If not, SAS will use the extra money you have to pay for sustainability investments.