The new Boeing 777X (777X) jetliner took to the skies today, entering the next phase of its rigorous test program. Based on the popular 777 and with proven technologies from the 787 Dreamliner, the 777X took off in front of thousands at Paine Field in Everett, Washington, at 10:09 a.m. LT for a three hour, 51 minute flight over Washington state before landing at Seattle's Boeing Field.

The first of four dedicated 777-9 flight test airplanes, WH001 will now undergo checks before resuming testing in the coming days. The test fleet, which began ground testing in Everett last year, will endure a comprehensive series of tests and conditions on the ground and in the air over the coming months to demonstrate the safety and reliability of the design.

The newest member of Boeing's market-leading widebody family, the 777X will deliver 10 percent lower fuel use and emissions and 10 percent lower operating costs than the competition through advanced aerodynamics, the latest generation carbon-fiber composite wing and the most advanced commercial engine ever built, GE Aviation's GE9X.

The new 777X also combines the best of the passenger-preferred 777 and 787 Dreamliner cabins with new innovations to deliver the flight experience of the future. Passengers will enjoy a wide, spacious cabin, large overhead bins that close easily for convenient access to their belongings, larger windows for a view from every seat, better cabin altitude and humidity, less noise and a smoother ride.

Boeing expects to deliver the first 777X in 2021. The program has won 340 orders and commitments from leading carriers around the world, including ANA, British Airways, Cathay Pacific Airways, Emirates, Etihad Airways, Lufthansa, Qatar Airways and Singapore Airlines. Since its launch in 2013, the 777X family has outsold the competition nearly 2 to 1.