World's biggest building is so huge it has its own weather and banks

The sprawling structure is large enough to completely contain Disneyland (Image: Boeing)

A factory spanning more than 472 million cubic feet is the largest building in the world – and is so big it could fit Disneyland inside. The gigantic Boeing Factory in Everett, Washington is 33% larger than its next-nearest rival, the Tesla Gigafactory, and over 5,000 wide bodied airliners have been built at Boeing’s massive factory since it opened in 1967. 

The giant facility occupies an area of 98 acres. For comparison, the original Disneyland park in Anaheim, California, spans about 85 acres.

The factory was originally built because Boeing’s then-President and Chairman of the Board, William M. Allen, recognised the need for an entirely new kind of factory to build its revolutionary new 747. The ”jumbo jet” was some two-and-a-half times bigger than the largest existing airliners of the day.

Various sites for the monster facility were considered, including a site in California, but the 747's head engineer, Joe Sutter, had reportedly opposed putting the facility so far away from Boeing's headquarters in Seattle, Washington.

Instead, the company selected a former military airport that was just 22 miles away from its HQ. Boeing’s first buildings on the site were used to construct the iconic B-17 Flying Fortress bomber during World War 2. The construction project was completed in record time, just over a year, at a cost of more than $1 billion — which was more than Boeing was actually worth at the time, according to Airways magazine.

Massive airliners are dwarfed by the colossal building (Image: Bloomberg via Getty Images)

While smaller construction projects might have one or two skips parked outside, Boeing had to move 4 million cubic yards of earth to build the plant, constructing a dedicated railway to shift all the waste material.

The result was a factory so huge that Disneyland could comfortably fit inside. It even had its own weather; when it first opened clouds would form just under its 90ft-high ceiling through a build-up of moisture. Now, though, air conditioning has prevented this from happening.

Bonnie Hilory, executive director of the Future of Flight Foundation, told the local Everett Herald that the factory is Boeing's “Best product.” She added: “I always tell people there’s one word to describe it and that’s scale. It’s just massive, with the biggest building, the biggest manufacturing and with giant aircraft inside of it.”

Boeing 777 freighters and 777X airliners being readied for their eventual buyers (Image: POOL/AFP via Getty Images)

The already-huge factory has undergone two major expansions: once in 1978 to accommodate production of the Boeing 767, and then again in 1992 for the even bigger Boeing 777. Recently, additional buildings have been added to the factory site to handle robotic assembly of the 777's fuselage and fabrication of the composite wing of Boeing’s new 400-seat 777X.

As of 2024, some 36,000 people are working on the 98-acre site every day, spread over three main shifts. Not all of them are working directly on aircraft construction. Some employees are working in the factory’s own dedicated fire department, banks, child-care facilities, medical clinic or water treatment plant. There are even full-time guides employed to lead visitors on tours of the factory.

Boeing Vice President and General Manager of the 777/777X program, Jason Clark, leading a press tour (Image: POOL/AFP via Getty Images)

The tours are hugely popular; 239,579 people going on the $20 (£15) tour last year. David and Georgiana King, from Sussex, have taken the tour twice – for the first time a decade ago and most recently in May 2025. “This place brought us out here,” David said. “It was some of the same as last time but the 787 has been introduced since we were last here so it’s interesting to see how technology has changed.”

While visitors are being led around the main shop floor, Boeing workers can get from one part of the building to another without getting in the way of aircraft production by using an elaborate system of tunnels that extend over two miles in length. There are over a thousand bicycles provided to help them navigate the tunnels. There are even a few vans being driven around the facility too.

Boeing employees work on a 777 (Image: POOL/AFP via Getty Images)

At ground level there are 12 push-button operated doors, the largest of which are 82 feet high and 350ft wide. 26 overhead cranes travelling 31 miles of track help guide the aircraft as they move along the assembly line at an average speed of around 1½ inches per minute.

The final stage of construction, painting the finished aircraft, takes up to seven days. A 747 required about 454 litres of paint while a 787 a little less at about 370 litres.

The whole operation is a slow and painstaking process. Boeing anticipates the first 777X will be delivered to customers in 2027. As of November 2025, there were 619 total orders for the 777X passenger and freighter versions from 12 customers.