It's official: Boeing 777X will take to the skies Thursday

UPDATE (Thursday, Jan. 23): Boeing delays first 777X flight

ORIGINAL POST: Boeing's updated 777 wide-body is set to fly for the first time Thursday, beginning a series of test flights needed before the aircraft can be certified for commercial service.

The flight is to take off around 10 a.m. local time (1 p.m. ET) at Boeing's assembly line facility near Everett, Washington.

The 777X is the latest update to the wide-body airframe that took its maiden flight in 1994 and first came into service about a year later with United Airlines.

Thursday's flight signals the start of "the next phase of its rigorous test program," according to Boeing spokesman Paul Bergman. But, he added, the flight could still get pushed to another day.

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"Flight testing is dynamic," Bergman wrote in a statement. "The date could change due to weather and other factors."

The test flight has already been delayed due to issues with General Electric's GE9X engines, which have had to undergo a redesign.

This newest version of of the 777 will be the biggest twin-engine passenger jet ever built, capable of seating well over 400 passengers for the larger variant, known as 777-9. The smaller 777-8 will be able to fly farther. Collectively, the two are referred to as 777X. Only the 777-9 has been built so far.

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Overall – at 251 feet, 9 inches for the bigger “dash-9 variant” – the 777X will be longer than Boeing’s current-generation 777 models.

Related:Video: Watch the Boeing 777X test aircraft stretch its wings

The 777X also will feature a wider wingspan. That’s led to what’s sure to become on of the jet’s signature features: folding wingtips. The jet’s wingspan of 235 feet is wider than any other Boeing – including the 747-8. It’s so wide that the 777X would face a tight fit finding a gate at some airports. But, with the wingtips folded up, the wingspan drops to 212 feet, 8 inches – an easier fit for when it needs to navigate to a gate at a congested airport.

Boeing's 777X will compete most directly with Airbus' new A350 model, though it likely will become a candidate for airlines looking to replace older aging older jumbo jets like Boeing's own 747 and Airbus' discontinued A380.

The European-produced A350 has already gained favor among passengers, and operates on high profile routes like Singapore Airline's nonstop to Newark, the current longest flight in the world. Boeing also lost out to Airbus when Qantas announced it favored the A350 for its proposed Project Sunrise flights, which would provide nonstop service from Sydney to New York and London.

The 777X's range is listed at about 8,400 miles (7,285 nautical miles) for the dash-9 model, according to Boeing. The dash 8 would have a range of about 10,000 miles (8,730 nautical miles).

The 777X's story is also inextricably intertwined with the ongoing 737 MAX saga. The 777X was rolled out to the public on March 13 of last year, the same day that the Federal Aviation Administration grounded the narrowbody in response to two crashes that combined killed 346 people.

The test flight will present Boeing with its first relatively high-profile opportunity to exhibit the renewed commitment to safe engineering its new CEO has promised. In the last few months, the manufacturer's safety culture has been under scrutiny as internal communications were released that showed employees questioning the safety of the jets they were working on.