Reduce taxi time,(for larger aircraft) continuous climb and decent, optimized flightpaths, implement greener lounges (green electric), more points for greener choices.

Bio fuel / green fuel as default, and having to pay more as a passenger if you want to fly on fossil based airplane fuel.

Plus tickets with discount if you don't want food or drink service

Earn EuroBonus points when recycling. Collaborate with apps such as Bower and Repeat in Sweden. They offer cash rewards for recycling. Why not reward points instead!

More efficient engines using sustainable aviation fuels combined with optimised flight paths and reduced taxiing time. Only use digital tickets.

Implement sharkskin technology or (my own) coating to reduce air resistance and micro-drag from the fuselage.