I would use my skills in optimization and deep learning to learn what frequenzies and time schedules that maximizes the load factor of each aircraft in the fleet.

Include meal information as early as possible in-app.
This is good for people with allergies, so they abstain from it.

Possibility to add transportation ticket to airport when buying a ticket from the Scandinavia's big cities. For example airport express train or flybus.

Let people on the plane as they are seated, start with A and F, then B and E, and then C and D at last.

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.

Higher prices to reduce number of flights