How Many Test Boeing 777X Aircraft Have Been Built?

The 777X is Boeing’s latest and greatest aircraft. The third generation of the record-setting 777 family, the aircraft first took to the skies in January 2020. While there have been delays in deliveries, Boeing has already begun building new units for testing. So how many 777X’s have already been built, and where are they going? Let’s find out.

The first Boeing 777X produced is registered N779XW and made the type’s maiden flight early last year, just two months before the pandemic shook the world. Photo: Boeing

All in

According to data from AeroTransport Data Bank (, Boeing has currently built four 777X’s. All of these aircraft have been involved in different tests for type certification, ranging from long-haul flying to cold soak testing in Alaska. All four of the jets made are of the larger 777-9 variant and will serve different parts of the type certification process.

The first 777X to roll off the production line was N779XW, which came in March 2019. After a secret unveiling to employees, test flights and the launch was pushed back a few months. However, on 25th January 2020, N779XW was revealed to the world on the type’s maiden voyage from rainy Paine Field in Washington.

Boeing 777X
N779XW made the 777X’s first flight debut. Photo: Jay Singh | Simple Flying

All registrations are under Boeing’s test numbers, starting with the US code ‘N.’ The four aircraft have been following a series, with 779X stating the aircraft variant (777-9) and W being the first plane produced. Once deliveries, all airlines will assign their own numbers in line with country rules.

N779XW is also designated WH001 and will be primarily used to test electronics, taxi tests, and the first flight, followed by avionics brakes, flutter, icing, stability, control, and low-speed aerodynamics.

Number two

Due to the pandemic and program delays, the second 777X only completed its testing in late April 2020. N779XX made its maiden test flight voyage on 1st May, joining the testing program for the type.

Designated WH002, N779XX is in charge of testing auto-landing, ground effects, stability, and controls. This has taken the plane on some interesting missions, including a 10-hour flight to nowhere for long-haul testing in different parts of the country.

The four 777X test aircraft all serve different roles in operations. Photo: Getty Images

Number three

The third 777X aircraft is registered N779XY and joined the program in August 2020. This plane is distinct due to its livery, which features an all-white fuselage instead of the blue on the other two.

WH003 will be used to test the 777X’s auxiliary power unit, avionics, flight loads, and propulsion performance. While it might be tested right now, N779XY has booked itself a future operator. The third 777X will go to Lufthansa, where it will carry passengers for decades to go.

Third 777X N779XY
After the 777X receives certification, N779XY is headed to Lufthansa for active commercial service. Photo: Lufthansa News via Twitter

Number four

The fourth and final 777X testbed joined the fleet in September 2020. The aircraft is registered (as you guessed correctly!) N779XZ. As the final test aircraft, N779XZ has some heavy lifting to do.

WH004 will be used to test environmental control systems, extended twin-engine operations (ETOPS), noise, and general functionality and reliability. This means the plane will likely be outfitted with passenger cabin technologies in the future. As if going in order, N779XZ is an all-white livery, with no blue tail either.

With all four test 777X’s in service, Boeing is going full steam with the certification process. While there have been delays recently, the aircraft remains on track for a late 2023 debut.

What do you think about the Boeing 777X test aircraft? Are you excited to fly the type? Let us know in the comments!