[17] In August 2017, the FAA issued the G500 a type inspection authorization to allow in flight evaluation.

[18] For the October 2017 NBAA show, the five G500s were completing their campaign with 995 flights and 3,690 h - 10 h 19 min for the longest - the first delivery schedule was maintained as certification was pushed until early 2018.

[22] As nacelle supplier Nordam filed for bankruptcy on 23 July, initial deliveries will be slowed.

[23] Certification allowed the EFVS to provide the only visual cues for landing down to 1,000 ft (300 m) runway visual range, to touchdown and rollout, after 50 test approaches, and testing to lower visibilities could allow dropping the limit.

[2][27] Four flight-test aircraft and a production G600 will be used for the test program for a scheduled 2018 introduction:[28] In August 2017, the fifth was being outfitted for its third quarter first flight.

[14] Through August 20, the four G600s have logged 780 h in 175 flights, the longest lasting 13 h 5 min, it completed testing for initial flight envelope expansion and flying qualities, flutter, brakes, low speed or stall, loads calibration, parameter identification and climb performance, the fifth test aircraft will fly later in the quarter.

[36] On October 4, 2021, Gulfstream introduced the 4,200 nmi (7,780 km) range G400, powered by Pratt & Whitney PW812GA engines with deliveries planned to start in 2025.

By March 2022, as the prototype was not yet rolled out, Gulfstream was anticipating a more extensive flight-test and certification campaign for the five test aircraft, as the G400 is powered by a different PW800 variant and the US government strengthened some certification requirements after the Boeing 737 Max groundings, but the 2025 first delivery goal remained.

[42] Both models have a four circular arcs cross-section fuselage, similar to the Gulfstream G650, with a 7 in (18 cm) reduction in width and height.

[44] The wing is a supercritical design with a 0.87 to 0.88 drag divergence Mach number depending upon lift coefficient.

The horizontal stabilizer, fairings, main landing gear doors, rudder and elevators, radome, rear pressure bulkhead and winglets are composite materials.

[41] The G500/G600 is powered by the Pratt & Whitney Canada PW800 series turbofan engines (PW814GA for G500 and PW815GA for G600) which was originally conceived for the Cessna Citation Columbus program.

The oxygen, cabin pressurization, landing gear control, aircraft health and trend monitoring systems are adapted from the G650.

[44] It is equipped with BAE Systems active sidesticks, appearing to be mechanically linked by being electrically back-driven, the first civil aircraft to be so.