isn't the real issue the space is limited because jet fuel is too expensive? Both in dollars to get it and cost to planet earth. Seems like the space available for seats per dollar spent will get much better with EPA or NPA ( https://news.ycombinator.com/item?id=21436838 ) and NPA with the stuff happening at places like https://terrapower.com/ seems very promising.
They figured out the $ they would save p.a with every change of page length, paper weight, etc. (it was partially offset by advertisers and onboard sales but not enough)
I can't recall the exact numbers but they were significant enough to warrant expensive external suits who eat their lunches at their desks doing the calculations and going ahead with it