Southwest in installing the Rockwell Collins Meridian in its 737 MAX 8 with
32" seat pitch throughout, 175 all Economy seats per aircraft.
AA 737-800s then are to have 172 seats, including MCE and F; 190 for the A321S and H, and LUS 321s as well. As has been discussed previously, IFE will be available on your device with onboard streaming WiFi, and power (universal AC and USB power outlets). The MAX 8 will include new, smaller lavs - I wonder if the old aircraft due for refurbishment will also get these?
Rockwell Collins says it's seats are so thin (lighter and smaller frame) that they "have 20% more living space" and that Meridian seat 30" pitch is like having one inch more than that, 31".
Update from The Points Guy (
link) 15 May 2018:
The first retrofitted “Project Oasis” 172 Seat 738 airframe (of 304) “has just entered service, with 12 more seats than the other 737-800s in the fleet. The aircraft registered as N979AN returned to Dallas/Fort Worth (DFW) from AA’s maintenance base in Tulsa (TUL) on Sunday May 13, ready to start flying revenue services after cabin modifications.”
Illustrations from TPG (seat chart from ExpertFlyer):