When you’re building some of the world’s biggest airliners, you need an equally outsized building.

When Boeing decided to build the 747 – a plane so big it would become known around the world as the jumbo jet – they had to build a factory large enough to build several of them at the same time.

If you’ve ever seen a 747 from close quarters you’ll know just how giant Boeing’s jumbo is. So it’s no surprise the factory which ended up building has to be very big indeed.

How big? Try the biggest enclosed building in the world.

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Boeing started work on the Everett factory in 1967, just as the Boeing 747 project was starting to gather pace. Bill Allen, Boeing’s charismatic chief, had realised the company would need a huge amount of space if they were going to build an airliner big enough to carry 400 passengers. They chose an area of woodland some 22 miles (35km) north of Seattle, near an airport that had served as a fighter base during World War Two.