(CNN) — Described as "the world's largest and most efficient twin-engine jet," the Boeing 777X was originally scheduled to enter into service in 2020, but the launch of the jetliner has been beset by delays.
Now expected to debut in 2025, the airplane's most striking exterior feature is undoubtedly its folding wingtips -- a first for commercial aviation.
But what will it look like from the inside? This month, Boeing proudly showcased a test-version of the 777-9X, one of two 777X variants, at the Farnborough Airshow, a UK-based aviation trade event, providing a hint of what passengers can expect.
The 777 has been a big success for Boeing since it began service in 1995, and remains the best selling wide-body aircraft. The 777X follows on from the popular but aging 777-300ER, and looks set to become one of the aircraft manufacturer's key airliners.
One of the most noticeable things about the experimental plane, aside from the fact that it's filled with monitoring equipment, is just how huge it is.
Visitors onboard the 777-9X, a test version of Boeing's 777X, during the Farnborough Airshow in the UK.
Justin Tallis/AFP/Getty Images
Measuring 251 feet, the aircraft can seat 426 passengers in a standard two-class configuration, and is longer than both its predecessor the 777-300ER (242 feet 4 inches) and the Airbus A350-1000, which has a length of just over 242 feet.
In the demonstrator plane, much of the space inside the cabin is currently taken up by testing stations, along with huge water tanks used to balance the aircraft during test conditions.
Although the aircraft has the same external width as the 777, its side walls are thinner, so there's enough room for 10 18-inch wide seats in economy.
Then there's the windows. Not only are they about 16% larger than those on the 777, they've also been installed higher on the fuselage to provide passengers with more natural light and a better view.
There were no overhead bins on show inside the demonstrator 777-9X, but Boeing has stated that those fitted on board will be able to hold twice as much as normal bins and require 40% less force to close.
According to Boeing, the best features of the 777 and 787 Dreamliner families have been brought together for the 777X, with added advancements, and the similarities are obvious.
The windows on the 777X will be around 16% larger than those on the 777.
Justin Tallis/AFP/Getty Images
"It has the same passenger features as the Dreamliner," explains Julie O'Donnell from the Boeing Commercial Airplanes Communications team. "So the LED lighting and the better humidity."
Like the Dreamliner, the 777X can maintain a lower cabin altitude of 6,000 feet, which "helps with fatigue," a member of the flight testing team tells CNN Travel during a tour of the aircraft, along with improved technology to "counteract turbulence."
The 775,000 pound plane is fitted with General Electric GE9X engines, the most powerful engines ever mounted on a commercial airliner. These burn 10% less fuel than those used on current 777s.
Inside the cockpit, the flight deck incorporates touchscreen displays that can support multiple touch points, allowing two pilots to interact with their section of the lower display simultaneously.
James Hanley, one of the test pilots on board the aircraft, was full of praise for the "modern" system, indicating that it's been a hit with pilots.
Rigorous test program
The plane's "modern" cockpit features heads-up displays.
One of the many controls fitted inside is used to operate the plane's folding wings, which have a span of just over 233 feet (71 meters).
The carbon-fiber-reinforced polymer wings were specifically designed to enable the aircraft to fit into the same gates, taxiways and runways as the 777.
While this design feature isn't unusual on Navy fighter jets built for landing on an aircraft carrier, this is the first time folding wingtips have been fitted on a commercial airliner.
The airliner's folding wingtips are a first for commercial aviation.
JUSTIN TALLIS/AFP via Getty Images
As a result, the US Federal Aviation Administration has drafted new regulations for the 777-9X and the 777-8X, its sister aircraft.
The 777-9 has been undergoing "rigorous" flight testing, both on the ground and in the air, and has been making good progress, according to the testing team.
The plane took its maiden flight back in January 2020 and now has more than 2,400 flight hours logged.
It wasn't just part of the static display at the first Farnborough Airshow to be held since 2019.
Attendees were treated to a spectacular aerial display in which the aircraft took flight at a near-vertical angle, before performing a number of impressive maneuvers, much to the delight of the crowd below.
"I never get tired of watching people see the airplane fly," O'Donnell told CNN Travel shortly before the awe-inspiring show.
The aircraft is now back at Seattle's Boeing Field, and has "resumed regular activities."
This latest high profile appearance comes months after Boeing announced that its delivery had been pushed back to 2025 due to "an updated assessment of the time required to meet certification requirements"
The aircraft soars through the sky during a demonstration flight at the Farnborough Airshow.
Justin Tallis/AFP/Getty Images
Boeing has received around 376 orders for the 777X.
Qatar Airways will be the first airline to receive the aircraft, according to Chief Executive Officer Akbar Al Baker, who told reporters at the Farnborough Airshow that he was considering putting in a "bigger order."
The state-owned flag carrier airline of Qatar went on to finalize an order for 25 of Boeing's 737 MAX 10 airliners, while Delta Air Lines announced that it plans to buy 100 of the largest variant of Boeing's 737 Max, which was also on display at the aerospace event. In March 2019, the MAX was grounded for 20 months following two fatal crashes. This was lifted in November 2020 after software updates and revised pilot training. Boeing Commercial Airplanes CEO Stan Deal says the aerospace company has received "strong demand" for the MAX since it returned to the skies.