[4] The 180-seat, 3,000-nautical-mile-range (5,600 km; 3,500 mi) airliner is designed to fly at 582 mph (937 km/h; 506 kn) within the capabilities of the Boeing 737 or Airbus A320 and could be in test service by 2027 at the earliest and 2035 at the latest.

The mounting of the engines at the rear end of the D8 instead of below the wings used in conventional aircraft design allows reduction of thrust requirements by minimizing inefficiency from boundary layer ingestion (BLI).

By ingesting and reenergizing the boundary layer flow, BLI reduces by 40% in the D8 the wasted kinetic energy in the combined high-velocity jet exhaust and slow-speed wake behind the fuselage.

Developed by United Technologies Research Center, a distortion-tolerant fan was scale tested at NASA and coped with flow distortion from ingesting the boundary layer close to the upper fuselage surface.

As a compact core limits blade tip clearances issues due to bending but cannot house the fan to low-pressure turbine driveshaft, Pratt & Whitney turned the core backwards, similar to PT6 arrangement, with hot gas discharged forward through a low-pressure power turbine connected to the fan via a short shaft and a gearbox.