The number of operating packs in cruise has more to do with revenue passengers' comfort than about saving fuel!
With 400+ breathing, heat generating pax in the cabin it's more about cabin air exchange rate [fresh air flow] than it would be, for example, when flying boxes in a freighter with only crew.
. . . Or will you be explaining to First Class passengers who fork over $4000 each for a seat why the cabin feels stuffy? . . . Because your company wants you to reduce cabin air flow to save fuel...?
