What Will The Boeing 777X Test Program Entail?

While the world waits for Boeing to get its 737 MAX certification back, we shouldn’t forget that we’re also waiting for another Boeing plane, the 777X, to take to the skies. Now we finally know what kind of testing the 777X is undergoing and how long it should take.

Boeing 777X Test Flight Getty Images
The first test flight of the Boeing 777X in January. Photo: Getty Images

Boeing has had a bit of rough time recently but they did get a spot of good news in January when the first test flight of the new 777X took off from Paine Field near Seattle. The flight was a success, but there are plenty more stages of testing to get through before the first delivery which is expected in 2021.

The test fleet

The first flight on January 25 was undertaken by the first of four test aircraft. According to Boeing, WH001 will be tested over the coming months for avionics and related system, brakes, flutter, icing, stability, control and low-speed aerodynamics.


This first aircraft will be joined in the coming months by three more planes for further testing. WH002 will be tested to ensure the auto-land, ground effects, stability and control are operational. This will be followed by WH003 which will be used to test the auxiliary power unit, avionics, flight loads and propulsion performance.

Boeing 777X test flight getty images
Boeing will need thousands of hours of test flights before certification. Photo: Getty Images

Finally, WH004 will test the environmental control systems, extended twin-engine operations, noise and general functionality and reliability. All four aircraft are expected to be flying in the first half of 2020.

If testing goes well certification would be due in January next year. However, Boeing has not confirmed any timelines other than that all four 777-9s should be in the air within the coming months.


Test flights

Before the 777X can be certified it needs to get several thousand hours of test flights under its belt. That means multiple aircraft flying several times a week. Test flights also don’t just mean a successful take-off and landing. Test flights are very complex and involved lots of variations and elements.

Initially, test flights prove that the plane flies the way it is intended to and there isn’t a major issue. But once that has been established things get more complicated. There are flights to test aerodynamic theories and fuel consumption. There are also advanced tests to check how the plane reacts to system failures and external elements such as strong tailwind or extreme temperatures.

All these elements are monitored by a team of engineers, mechanics and pilots on board the aircraft during the test flight. Every part of the aircraft’s system is tested by computers and monitors check performance for the duration of the flight.

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An example of equipment used to test aircraft on a Boeing 747. Photo: Getty Images

They also carry out extreme tests such as full-force breaking during take-off as well as seeing how slowly the aircraft can go while still flying. These tests should ensure that once certified the aircraft is ready for any situation and not just the day-to-day activities.

Lessons learned

Most of the aviation world will be watching Boeing’s test procedures very carefully after the fiasco with the MAX. But Boeing insists the 777X will be different. In a statement, Boeing confirmed, “We’re taking the lessons learned from the 737 Max and applying them to the 777X to ensure we are as prepared as possible for 777X certification”.

As the 777X does not have the MCAS software, it is likely that although inspections will be rigorous, testing should be successful. Additionally, Boeing will certify the 777X as a variant of the existing 777 and not as a new aircraft. With just over 300 aircraft already ordered from the likes of British Airways, Emirates Airways and Qatar Airways, Boeing is no doubt hoping for smooth sailing through the testing phase.


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Mark Thompson

The interior of these planes does not look very comfortable. Oh how I long for the days of luxury when Pan Am was still flying.

High Mile Club

I believe the fact it doesn’t have MCAS should be plastered everywhere so everyone stops asking if it does. I understand that not everyone knows that MCAS was largely influenced by the lack of ground clearance on the 737 for the new engines, but it SHOULD be understood that the GE9X is only 10 or so inches bigger in diameter when compared to the GE90-115. The 747-8 shows 787 tech works better on larger aircraft than it does with smaller ones, and while the 777x was designed and built while the MAX was in development, the project was delayed quite… Read more »


HMC – it’s that old double edged sword you referenced; Since the flying public doesn’t generally know/care what aircraft they are on (remember cheapest ticket?) they don’t have the knowledge to know the difference between a 737 Max and a 777X. They hear a little chatter about Boeing/MCAS/Grounding and they leap to conclusions

High Mile Club

All the more reason to make it so clear it’s painful to read. No one can be that stupid to not understand how size matters.


I’m interested to know whether any other certifying body will retest the airframe to see if it can actually achieve the required test standard, which it spectacularly failed to manage back in November…. as it looks like the FAA is fine with it failing the test.?


I thought, perhaps mistakenly, that a substantial part of the reason why the B777X had taken so long in development, was that it had essentially a new, mostly composite fuselage, combined with an almost completely new wing & brand new engines, especially developed for this particular airframe.???

Assuming my assumptions to be correct, exactly how will the company manage to convince first the FAA & then the rest of the Worlds’ certifying bodies that; “Boeing will certify the 777X as a variant of the existing 777 and not as a new aircraft”.?

…..just asking.?

High Mile Club

It’s just the wings and some engine parts that are composite. The fuselage is still full aluminum.


How much of the wings.?
I was under the impression they were ‘all-new’ as they’re that much bigger than the ‘old’ ones.
Also, the engines have been lot’s of trouble because they’re all new. I’m not bothered about whether there’s composites in them, that’s normal these days. I’m concerned that they’re a part of a mostly new airframe that’s being passed-off as the same as the older version……….
In exactly the same way Boeing did between the 737-NG and the MAX…….. with very unfortunate consequences.

High Mile Club

Should i just tell you the simple answer or should I tell you to go onto Google and look it up yourself? We’re on the internet; all these questions you’re asking you can research yourself. You can’t call yourself an avgeek if you can’t do some simple background searching.


HMC, Just making conversation…… Having read-up a little….. (I was hoping someone else would do the legwork for me.!) it seems that the fuselage is exactly the same design as before, but has been stretched considerably. The engines are new, but based-upon the previous B777 design. Just much more massive & effectively all new, because whilst the design is ‘old’, GE have never built an engine of anything like this size before (nor has anyone else.!!!) The wings are almost entirely new, with a different areodynamic aspect & constructed almost entirely from composites AND including the 3.5 meter folding tips.… Read more »

High Mile Club

No one is going to want to give anyone info that people can easily find themselves. Any time someone comes out with actual information, there are always going to be people who will deny it’s worth. That’s why I encourage people to actually do the research themselves; all the information at our fingertips, yet no one looks it up. That’s why we have people who think the 787 only has one engine option, simply because the Trent 1000 has been in the news a lot. As for the fuselage, there may be new aluminum alloys used in it, but it’s… Read more »

Gerrard White

I think that you are right – there has been a lot of discussion as to whether the same fundamental problems as arose with the Max, that is to say too many changes to not inflect every aspect of performance and safety and so impose a new plane certification, or can allow for ‘grandfathering’ and certification as a variant. The journalist above says ‘Boeing will certify the 777X’ which seems mistaken, or a slip of the tongue, or in fact a credulous belief in Boeing PR. In any case at least Emirates have said enough is enough and they will… Read more »


EASA will never again grant certification to another Boeing product if it competes with an Airbus product.

High Mile Club

I’m pretty certain A LOT of European airlines will riot about how much that will affect their business.