Dynamic seating - people with checked in baggage should be placed towards the rear of the plane as they are more likely to have to wait anyway on arrival at destination.

Urban farming/green house/open oasis at CPH. Be the first to serve “hub grown” veggies in the sky.

Collaborate with public transport companies at popular destinations to reduce car usage.

Weigh all passengers anonymously to optimize fuel load for best performance.

Make the app as lightweight as possible. Remove images, animations and leave only the bare necessities. This saves data transfer and storage - which in turn saves energy.

Nuclear fuel last for much longer than fossil, and a plane can fly as long as it,s food for, so around the world in one flight.

It's also good for noise pollution