[paganholiday]

Traditional jets have a long inventory and regulation cycle but for example retrofitting a A320 to LNG appears to save 20%:

https://repository.tudelft.nl/record/uuid:63b89022-ac68-426d...

Which still puts it behind the 787 let alone the generation that comes next.. But you aren't going to succeed at making any new inventory without every possible efficiency improvement to drive sales and retirement of older inventory.