The changes for 777X include General Electric GE9X engines, composite wings with folding wingtips, greater cabin width and seating capacity, and technologies from the Boeing 787.

As of September 2024[update], there are 503 total orders for the 777X passenger and freighter versions from thirteen identified customers and unnamed buyer(s).

Deliveries have been delayed multiple times; as of January 2025, Boeing expects the first aircraft to be delivered in 2026, to the launch customer Lufthansa.

In 2011, Boeing refined its response to the revamped Airbus A350 XWB with three 777X models, targeting a firm configuration in 2015, flying in late 2017 or 2018, and entering service by 2019.

Early designs of the smaller 353-seat 777-8X proposed stretching the 777-200ER by ten frames to a length of 228 ft 2 in (69.55 m), with a 694,000 lb (315 t) MTOW and 88,000 lbf (390 kN) turbofans to compete with the A350-900.

[21] The -9 firm-configuration was reached in August 2015 and assembly of the initial aircraft was to begin in 2017 for a December 2019 introduction advanced from the previously scheduled 2020.

[24] The assembly of the first composite wing test example began in Everett in late September 2017 with its top section lowered into a jig for robotic drilling.

[25] Boeing launched the 777-9 production on October 23 with the wing spar drilling; its maiden flight was scheduled in the first quarter of 2019, one year before its introduction, perhaps with Emirates.

The Fuselage Automated Upright Build (FAUB) system was developed and quietly tested in Anacortes, Washington, 40 miles north of the 777 Everett assembly plant.

A major leap in automated production, it drills the tens of thousands of holes in the fuselage more quickly, accurately, and safely.

[29] In February 2018, Subaru (ex–Fuji Heavy Industries) completed the first aluminum and titanium center wingbox integrated with main landing gear wheel wells at its Handa factory.

Wing assembly is difficult, with the light but strong carbon-fiber material being less forgiving than traditional aluminum, and aircraft systems integration in a special demonstration lab is not as quick as planned.

[34] In May 2018, Qatar Airways head Akbar Al Baker thought development was a couple of months late but expects Boeing to catch up, provided no certification issues arise.

To position wings and fuselage sections, automated guided vehicles are replacing overhead cranes and "monuments" - large, permanent tooling fixtures.

[52] GE Aviation in Ohio is recalling four GE9X turbofans from Boeing in Washington state in Antonov An-124 freighters from Volga-Dnepr Airlines, mounted in 26 x 14 x 13 ft (8 x 4 x 4 m), 36,000 lb (16.3 t) stands.

[54][55] Depending on the outcome of its root cause investigation, Boeing should have time to modify the failed part and repeat the test during the margin from the existing engine-related delays.

[57] In October 2019, the JATR board created to review the Boeing 737 MAX certification noted that the FAA would need to assess more thoroughly how modifications interact with the aircraft.

The 777X was already a year behind schedule as service introduction was targeted for 2022, a further delay due to the certification as a derivative could risk key orders.

[62] Boeing stated that the 777X does not have an equivalent of the Maneuvering Characteristics Augmentation System (MCAS) that is installed on the 737 MAX and that played a role in two crashes.

[66] On June 27, 2021, The Seattle Times reported on an FAA letter to Boeing dated May 13 delaying type certification until mid to late 2023, pushing deliveries to 2024.

[74] On October 11, 2024, Boeing confirmed that the expected first delivery of the aircraft had slipped to 2026, following development challenges and workplace strikes at the company.

[76] Flight testing resumed on January 16, 2025 following grounding in August 2024 due to cracks discovered in engine mounting hardware.

[81] The mechanism was demonstrated for Aviation Week at the Boeing Everett Factory in October 2016; the folding movement should be complete in 20 seconds and be locked in place at the end.

[83] As existing regulations do not cover the folding wingtips, the FAA issued special conditions, including proving their load-carrying limits, demonstrating their handling qualities in a crosswind when raised, alerting the crew when they are not correctly positioned while the mechanism and controls will be further inspected.

[85] Transported by sea from Subaru in Nagoya to Everett, the center wing-box is similar in size to the legacy 777 but is more reinforced and heavier, with more titanium.

[97] Boeing also proposed an interim solution to Qantas, assumed to comprise a 777-9 with auxiliary fuel tanks and reduced seating capacity.

[citation needed] In June 2019, Qatar Airways urged Boeing to develop a 777X-based freighter to replace its existing 777Fs which were first delivered in 2009.

[102] On January 31, 2022, Boeing officially launched the 777-8 Freighter, with an order from Qatar Airways for 34 aircraft and 16 options, with deliveries expected to begin in 2027.

Etihad's widespread investing strategy had backfired as it reduced feed sources, making it harder to fill the orders for the 777X.

[134] On December 19, 2024, China Airlines announced plans to order ten 777-9s to replace their existing 777-300ERs along with four 777-8s to supplement their freighter fleet.