Washington, Jan 26 (IANS): Boeing 777-9X, the world's longest and largest twin-engine airliner, has completed its maiden test flight, the American aircraft manufacturer announced.

The aircraft, which took off from Everett, Washington state, flew almost four hours before it landed at Seattle's Boeing Field on Saturday, the company said, adding that two prior test attempts were called off due to high winds this week, reports Xinhua news agency.

"Today's safe first flight of the 777X is a tribute to the years of hard work and dedication from our teammates, our suppliers and our community partners in Washington state and across the globe," said Stan Deal, Executive Vice President of Boeing and President and CEO of Boeing Commercial Airplanes.

The 777X plane, with two foldable wings spanning more than 235 feet, is the world's largest twin-engine commercial aircraft.

It is 10 per cent more cost-effective and 10 per cent more fuel efficient.

Boeing said it expects to deliver the first 777X aircraft in 2021 after receiving orders from the world's leading air carriers, including Japan's All Nippon Airways, British Airways, Cathay Pacific Airways and Singapore Airlines.

The company said earlier this month that it delivered a total of 380 commercial airplanes in 2019, its lowest number since 2008.

The figure fell by 53 per cent compared with the previous year.

The company's poor sales record was attributed mainly to the 737 MAX crisis, after two of the jets were involved in two fatal crashes in October 2018 and March 2019, which killed a total of 346 people in Indonesia and Ethiopia.

All MAX aircraft have been grounded globally since March 2019.

Their return to service has been delayed several times after Boeing failed to obtain certified approval from US federal regulators.