A Boeing 777X airplane takes off during its first test flight from the company's plant in Everett, Washington, U.S. January 25, 2020. REUTERS/Terray Sylvester

SEATTLE (Reuters) - Boeing Co BA.N on Saturday successfully completed the maiden flight of the world's largest twin-engined jetliner, the 777X.

The 252-foot-long passenger jet landed at Boeing Field near downtown Seattle at 2:00 p.m. local time (2200 GMT) after a debut of more than three hours marking the start of a year of testing before it enters intercontinental service in 2021.