. . . which Boeing promises will be 'the largest and most efficient twin-engine jet in the world'

The first assembled 777X jetliner has rolled off the Boeing production line at the manufacturer's Everett factory in Washington state.

Pictures show a 'static' 777X in a hangar at the gigantic factory.

This means that this particular 777X isn't destined for the skies but will be used for a year-long series of tests in a nearby building.

The first assembled Boeing 777X jetliner has rolled off the production line at the manufacturer's Everett factory in Washington state

Boeing claims that the 777X will be the largest and most efficient twin engine jet in the world, with 12 per cent lower fuel consumption and 10 per cent lower operating costs than the competition.

Its features include folding wing-tips – the 235ft wings are the biggest Boeing has ever made, over 30ft longer than the current model's wingspan – bigger windows and overhead bins compared to the current 777 and 'advanced LED lighting'.

There will be two versions of the 777X - the 777-8 and 777-9, costing $360.5million and $388.7million respectively.

The 777-8 will be able to seat between 350 and 375 passengers and the 777-9 between 400 and 425, depending on the buyer's layout requirements. In comparison the current family of 777s offer capacities of between 300 and 370.

There is also an improvement with range. The 777X can fly for 16,110km (10,010miles), compared to the 777's maximum range of 15,800km (9,817miles).

'After years of hard work it is exciting to see the static airplane come together,' said Danielle Hovington, the Structures Engineering lead who worked on the static airplane. 'This is just the beginning – with testing expected to start in the next few months, the rewarding part of the job is yet to come.'

Although 777X testing has been underway since 2015 in lab environments, wind tunnels and simulations, a full-scale airplane is needed to verify the design strength and the accuracy of the analytical model used during design.

'Static test is our opportunity to verify the design of the structure and load bearing components of the airplane, ensuring the final product is safe for our customers and the flying public,' said Doreen Bingo, Boeing Test & Evaluation 777X Test Program manager. 'Using a full-scale airplane, we'll run various load conditions on the wings, gears, the struts and the fuselage.'

Boeing claims that the 777X will be the largest and most efficient twin engine jet in the world, with 12 per cent lower fuel consumption and 10 per cent lower operating costs than the competition

This is an image of the current standard 777, which has become one of the world's most commercially successful airliners

During previous static testing, wings have been tested at 150 per cent of the designated load, resulting in a wing flexing more than 26 feet.

Testing is scheduled to begin in late 2018 and will run for one year. Flight test airplanes are in production now, with the flight test program to begin in 2019. Deliveries to customers are expected to begin in 2020.

The carriers that have placed orders are All Nippon Airways, Cathay Pacific, Emirates, Etihad Airways, Lufthansa, Qatar Airways and Singapore Airlines.

Boeing told MailOnline Travel: 'The 777X builds on the passenger-preferred and market-leading 777.

'The 777X will include new engines, an all-new composite wing and will leverage technologies from the 787 Dreamliner.

'The 777X family includes the 777-8 and the 777-9 – both designed to respond to market needs and customer preferences.

'The 777-8 competes directly with the A350-1000, while the 777-9 is in a class by itself.'