By reducing the time planes spend with engines idling on the ground, we can decrease fuel consumption and emissions.

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.

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

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

Reduce cup size with 5-10%, and stop giving napkins as a default

Allow free rebooking on the day of departure to a shorter route or a route with less stops when available, even in low booking classes and without status.