If you reduce the allowed weight for luggage from 23 kg to 15 kg or so, people might start to think if they really need all that stuff with them.

Flyers sponsor local green projects tied to their flight emissions, receive progress updates, and earn rewards, creating real community impact and emotional connection.

Reusable boarding cards for people without phones. Like the consius travelee bag tag.

Voluntary fee of 5 cent/mile that goes to research and developement all electrical passenger airplanes. The aircompany gives another 5 cent per same miles.

Giving an incentive and getting more passengers to travel light should reduce aircraft loading and fuel consumption. Alternatively allow more cargo.

Create an ability to share a seat in your car with other passengers on the flight. It's better than everyone riding their car.