Better food = less food waste. I see a lot of boxes not being emptied. So make sure it's good quality food to most peoples liking. Keep it simple and good

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

Encourage food suppliers and distributors to use more sustainable and healthy packaging in the food that gets served.

Sell tickets without any luggage.

Instead of "I don't want to earn any points on this trip", make the customer choose between earning points or donating points to charity

My personal CO2 emissions should be listed on my boarding pass in the app for each flight.