Encouraging standardized suitcase measurements and/or using AI to plan and stack luggage for saving space and even out the plane in regards to weight.

Cut the knives and fork in the breakfast box, we only need spoon for yoghurt. There's no need for one glass per item

Arrange crew accommodations closer to airports to reduce transportation emission

Taxiing from and to gates from runways should be more smooth and with less fuel - using for example AI

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.

Make a “code-share” cooperation with train providers, to allow for booking a ticket from A to B with combined train-plane modality and same benefits as connecting flight