In a recent letter on the subject of "Post month look-back", our Crew Resources Guru finally admits shorter trips are cheaper for Delta to cover . "Because of the analysis we've done we see benefit in shorter trips, but have a difficult time building them because of the confluence of how the network flies (structure of banks, time channels covered, pace of the recovery, etc.) and the rules that generate credit, efficient legs are being consumed into longer rotations to offset these challenges." So as we've suspected for ten years now 4 and 5 day trips are more EXPENSIVE for Delta to operate. Delta operates more expensive trips either because they can't "figure-out" a better way to construct the trips or some ulterior motive? So not only are the current trip selections miserable for flight crews, they are more EXPENSIVE for Delta to cover.