The fifth Boeing 777-9 prototype has performed its first flight, taking off from Boeing’s Everett facility and completing a routine test circuit over Washington state. This milestone adds to the diversity of the 777X flight test fleet, which began flight in January 2020. WH015 is the fifth of the six airframes scheduled to fly as part of the delayed and highly scrutinized 777X certification program.
On August 2, 2025, the aircraft departed Paine Field (PAE) and landed safely at Boeing Field (BFI) in Seattle after a several-hour functional check flight. While Boeing officials have refused to comment publicly about the plane’s exact configuration, airplane spotters noted that the jet, with Boeing’s classic 777X livery, had slight instrumentation differences from earlier test aircraft, perhaps indicative of its testing intent.
With the addition of the fifth Boeing 777X aircraft, Boeing continues working towards certifying the new generation widebody plane by 2026. The fifth Boeing 777-9 adds testing capabilities for various flight conditions, avionics systems, and long-term operational scenarios that regulators will closely monitor over the next few months.
Fifth Boeing 777X Maiden Flight
The aircraft, registered as N779XX, took off from Paine Field (PAE) at 09:51 local time on August 5, and returned after 2 hours and 27 minutes of flight testing. This is Boeing’s fifth 777-9 test aircraft and was initially painted in full Singapore Airlines livery in late June.
Moreover, this particular airframe is destined to become Singapore Airlines’ first Boeing 777X, marking a major milestone for both the airline and the program. As the launch customer in Asia for the 777-9, Singapore Airlines is expected to be one of the early operators once the type is certified.
Although the fifth flight test aircraft has arrived later than originally planned, initially scheduled to fly in 2023, it arrived when Boeing is taking a breather from a succession of 777X program challenges and controversy regarding overall quality control issues.
A Closer Look at the WH015 Test Aircraft
Boeing typically designated each 777X test aircraft with a unique code i.e. WH001 through WH015, which indicates individual build numbers and test objectives. The fifth Boeing 777-9, WH015, seems structurally the same as its siblings but may have newer software or component tweaks meant to simulate the last customer version.
Earlier 777-9 test aircraft have been used for numerous test objectives:
- WH001 largely focused on flight characteristics and flutter testing.
- WH002 and WH003 performed avionics, environmental, and system verification.
- WH004 performed interior and cabin system assessment.
Moreover, the role of WH015 can be an extension of the above operations or tailored to perform tests for long-haul reliability, ETOPS, or certification adjustments specific to international regulations like EASA.
Boeing 777X Program: Slowly Gaining Altitude
The Boeing 777X program had a long and turbulent journey. Originally launched in 2013, the twin-jet was originally planned to enter service in 2020. However, delays on engines, design alterations, updates to FAA regulations, and fallout from the 737 MAX debacle later bumped the program well beyond its initial expectation. Boeing is aiming for the first delivery in 2026, with launch customer Emirates expected to be among the first to receive the aircraft.
In spite of the setbacks, it is still Boeing’s most ambitious twin-engine widebody with the established 777 fuselage combined with the new GE9X engines, carbon-fiber composite wings, and foldable wingtips. The aircraft is designed to provide improved fuel efficiency as well as range and capacity improvement, attributes which would appeal to airlines capable of operating high-demand long-range routes.
With the addition of the fifth Boeing 777-9 to test fleet, it is a boost for the concluding leg of certification, especially at a time when Boeing needs to have positive program milestones to recapture market confidence.
What’s Next for the Boeing 777X?
With WH015 operational, Boeing can now speed up the envelope growth testing and validation of software updates, avionics redundancies, and system reliability at longer flight durations. Certification has become more stringent since the 737 MAX, with rigorous documentation and real-world performance data demanded.
The Federal Aviation Administration (FAA) and international regulators elsewhere will draw on testing data from all five flight test aircraft. The testing data will be used to assess airworthiness, robustness, and passenger safety before issuing final type certification.
Simultaneously, Boeing is also designing the 777-8, a shorter, longer-range variant of the 777X family, which may serve the ultra-long-haul market. However, the 777-9 remains the immediate priority, given it has the bulk of existing orders.
As of August 2025, Boeing has firm orders for over 555 777X aircraft from global carriers including Emirates, Qatar Airways, Lufthansa, Cathay Pacific, Singapore Airlines, and All Nippon Airways.
Aviation Community Reaction
Avid aviation followers and industry watchers quickly picked up on the flight on tracking sites like FlightRadar24, with many commenting on the symbolic importance of the fifth Boeing 777X finally flying. The successful first flight of the aircraft is seen as a positive signal that Boeing is regaining control of the 777X program and entering the final phase of testing.
As Boeing accelerates development amid increased FAA oversight and global regulatory expectations, WH015 will likely play a central role in proving the aircraft’s readiness for commercial service in a post-pandemic aviation market looking for efficient, high-capacity widebodies.
Bottom Line
Boeing’s largest twin-engine jet program has another milestone with the fifth 777-9. Having flown for the first time, the plane will now furnish key test information into the certification path and drive Boeing toward the delivery of the next-generation 777X.
Even though, the program has experienced delays, but the incremental development of the flight test fleet is now beginning to gain traction alongside investor and customer confidence.
