United Airlines is working on a lie-flat premium-cabin seat and plans to have the first ones in service on Boeing 737-10s sometime in 2020, United president Scott Kirby said.
The seats would be installed on a subfleet of the carrier’s 737-10s. United has 100 737-10s on order as well as 14 737-7s and 41 737-9, Aviation Week Fleet Discovery shows. It has six 737-9s in service.
Collected and summarized from the source below by Giang Tan http://atwonline.com/aircraft-interiors/united-plans-introduce-737-10-lie-flat-premium-seat-2020