EVERETT, WA—Boeing recently announced that the major fuselage sections of the first 777X test aircraft have been joined together. This assembly milestone, called the final body join, occurs when the airplane’s nose, mid and aft sections are connected.

The first 777X introduced will be the 777-9 model, which can seat 400 to 425 passengers in a standard configuration and offer a range of 7,600 nautical miles. Its first flight is scheduled for 2019, with the plane expected to enter service in 2020,. A smaller variant, the 777-8, is set to follow a few years later.

The 777x is 252 feet long, making it the longest passenger jet that Boeing has ever produced. The twin-engine jet is also the first to feature folding wingtips, which, when extended in the air, will give it a wingspan of 235 feet.

Boeing says the 777x, which is powered by the GE9X engine, will consumer 12 percent less fuel and be 10 percent cheaper to run than similar competing airliners. The aircraft’s new composite folding wings have been developed so it can fit in the same airports and gates as Boeing’s current popular long-range aircraft, the 777-300ER, while delivering these savings.