In Scandi all tap water is great. Sell SAS water bottles onboard which are made to be reused = able to buy for points, pre-order as well. And then load tap water onboard.

Use more big size bottles and not small cans/bottles

Allow users to visualise their travel carbon footprint in-app. Include everything such as transportation to/from the home and destination, hotels.

Make flight space available for package distributors ex. DHL for a fee. Might save their flight and truck if packages can go with regular airplanes.

Pay for luggage by weight.

Do not carry tax-free goods on flights. Use as online service and if necessary in partnership with partners allowing pick-up at airports.