When the crew collects trash before landing, why not make separate rounds for collecting, cans, plastic cups, paper, etc instead of collecting all trash in the same bin.

Drop food and snack service on all domestic flights (<1 hour), only coffee, tea and water. Both plus and go

Using hydrogen tanks in the rear of the plane, for example. This could work on shorter routes such as domestic flights or intra-Europe.

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

Pay for luggage by weight.

Develop lightweight, recyclable cabin materials and onboard items to reduce aircraft weight and waste.