@whitequark If you follow the breadcrumbs, it leads to IATA RP 1726 by way of https://github.com/google/travel-impact-model , which prescribes a cabin class factor with very little justification. Despite the lack of concrete justification, this is an industry publication, and I don't think it's unreasonable to use their own best practices in lieu of a better model.
I don't see how you can argue that business/first is equally efficient to economy, so on what basis would you prefer to reconcile that? Are you trying to argue that because business seats exist on the plane, you shouldn't be responsible for their contribution to reduced per-pax efficiency if you use one...?
