I don't see it as a way of decreasing costs as much as a way to improve aircraft and facility utilization.
Depending on the staffing level, AA may be viewing it as a way to improve throughput/output by anywhere from 15-30% without having to add additional infrastructure. Airplanes don't make money when they're chocked or on jacks...
Ok staffing level. There are not enough mechanics to cover the amount of work. Engineering does not effectively support the mechanics. Stores is barely available. Boeing takes to long to respond to OH. Supervisors are working longer shifts. Managers having most of the weekends off, although some are seen on the weekends. Morale is at an all time low. A 22 day RETRO with corrosion ending up in the 40+ day check. "Level Loading", now thats funny. A 600k est. check costing 1.2 to 1.3 Million.
Seven day coverage is what you make of it, and there may be enough people who find it appealing to make it work well for both sides.
There are not enough people to work it. Placing one aircraft dock out of four on 7-day coverage, while allowing the other three to work 5/8's and OT on SAT/SUN. Whole crew attempting to bid off of the one dock.
I went to seven day coverage in my IT shop a few years back, and saw immediate benefits. Defects dropped (no more rushing on Friday to get things done before quitting time), service levels increased (no need to wait for someone on a weekend "drop-in"). That in turn decreased workplace stress, especially knowing that there would be fewer weekend call-outs.
"Defects" soaring, cost increasing and more paperwork than ever. Q/A schedules not matching that of the mechanics.
Programmers were on salary and non-union, so admittedly different economics apply. But there was no shortage of people willing to have Fri-Sat or Sun-Mon as days off, either.
There is a shortage of people at TULE and again those are trying to leave.
When I lived in NYC, having Sun-Mon was the best of both worlds for days off. One weekend day off to do things with people who had a regular workweek, and one day off to do doctors appointments, banking, etc. when they were open. Maybe things have changed, but in the early 90's, getting a Saturday doctor or dental appointment on Long Island was impossible.
In DFW, having Fri-Sat off was perfect. Was able to leave for Chickasaw on Thursday night to grab a good campsite, fish all day Friday without dodging Jetskis and speedboats, and then beat traffic by leaving first thing Sunday morning (and still make it to work) or late Saturday night. Would have also made it really easy to do all the kid stuff like soccer, etc.
I know there are a few who find anything other than bankers hours to be abhorrent, but I actually miss shift work and mid-week days off...