Boeing Co has successfully completed the maiden flight of the world's largest twin-engined jetliner as the embattled planemaker steps up competition with European rival Airbus in a respite from a crisis over its smaller 737 MAX.
The 777X, a larger and more efficient version of Boeing's successful 777 mini-jumbo, took off outside Seattle on Saturday at 10:09am local time and landed at 2pm.
Two earlier attempts were called off this week due to high winds.
Boeing officials said the maiden voyage would herald months of testing and certification before the aircraft enters service with Emirates in 2021, a year later than originally scheduled because of snags during development.
The aircraft is the larger of two versions planned by Boeing and will officially be known as the 777-9, but is better known under its development codename, the 777X.
Its most visible features include folding wingtips - designed to allow its large new carbon-composite wings to fit into the same parking bays as earlier models - and the world's largest commercial engines, built by General Electric and wide enough to swallow the fuselage of a 737 MAX.
The successful flight was a boost for Boeing as it grapples with a broadening crisis over the 737 MAX, which has been grounded since March following two fatal crashes.
"To me this is the flagship for the big airlines around the world ... it represents the great things we can do as a company," 777X marketing director Wendy Sowers told reporters when asked about the flight's importance in light of the MAX crisis.
Boeing says it has sold 309 of the aircraft - worth more than $US442 million ($A648 million) each at list prices - but analysts have questioned its heavy reliance on Middle East carriers that have scaled back purchases as they suffer a pause in their expansion.
The 777X will compete with the recently introduced Airbus A350-1000 which seats about 360 passengers. Both reflect the growing range and efficiency of twin-engined jets that are steadily displacing their older four-engined counterparts.
The two planemakers have clashed over the relative efficiency of their latest jets but both face worries about demand due to overcapacity and signs of weakness in the global economy.
Australian Associated Press