EVERETT — People from all over the world visit the Future of Flight Aviation Center every year to go on the Boeing Tour.

The 90-minute tour allows visitors to see inside the Boeing factory in Everett and peer down from open-air observation decks as 747, 777, and 787 planes are being built.

“It’s our best product,” said Bonnie Hilory, executive director of the Future of Flight Foundation. “I always tell people there’s one world 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.”

The Boeing Co. started conducting official tours in 1968, shortly after production of the first 747s began, according to Sandy Ward, marketing director for the Future of Flight Aviation Center and Boeing Tour.

A total of 39,401 people visited during the first year of the tours. The first permanent tour building center opened in 1984 and was used until December 2005 when the Future of Flight Aviation Center &Boeing Tour opened at 8415 Paine Field Blvd.

The most visitors from other countries come from China, Japan, Australia and Germany. About 37 percent of visitors come from Washington. Overall attendance has grown every year, with a record number of 239,579 people going on the tour last year.

“We have grown at an average rate of 15 percent per year,” Ward said. “(The Boeing Tour) gets great reviews. It has become a must-do attraction.”

An adult reserved tour ticket during peak season costs $18 while a walk-up adult ticket is $20.

Tickets for children ages 15 and younger, who are at least four feet tall, are $12 if reserved and $14 for walk-ups. The demand for the tour is so high during the summer months that four new tour slots have been added starting July 1 to accommodate up to 2,000 daily visitors.

The Boeing tour begins with a short film in the Boeing Theater.

Everyone is then shuttled by bus to the Boeing factory. During the drive, tour guides speak about the company’s founder, William E. Boeing, who initially dropped out of Yale University to take part in the timber industry.

Groups arrive at the factory and walk through part of the 2.33 miles of tunnel to a freight elevator.

Once inside, a tour guide tells visitors that they are in the world’s largest building by volume, at 472 million cubic feet. The size is large enough to fit all of Disneyland and 12 acres of parking.

The elevators doors open again to an observation balcony that features a cross-section of a 747-100. Visitors can then walk along a balcony and take in views of 747-8s being built.

From here, the tour groups are taken outside, directed to get back on a bus, and shuttled to another part of the Boeing factory in order to view assembly work being completed on 777s and 787s from another observation balcony.

At the end of a tour in May, visitor Sandra Hook from Sydney, Australia, returned to the Future of Flight Aviation Center and walked straight into the Boeing Shop.

“I have a father back in Australia who is very keen on aeronautical information so we just raided the shop,” she said. “(The Boeing Tour) was a great opportunity to see the size and scope of the operation and just to see how exacting it is to put together these planes that have millions and millions of bits that are flown in from all around the world.”

The information provided throughout the tour was informative, said Dorinda Duty of Hemet, Calif.

She added that the best part was her guide’s sense of humor and that she enjoyed hearing that there was a weather spotter in the building after it was newly built because clouds formed near the ceiling.

The problem was fixed when an air circulation system was installed.

Her husband, Dan, remembered another one-liner he heard while on the tour.

“If it’s not Boeing, I’m not going,” he said.

David and Georgiana King’s second Boeing Tour experience was made complete with a visit to the Future of Flight’s Strato Deck.

The couple from Sussex, England, first went on the Boeing Tour a decade ago.

They took the tour in May as part of their 25th wedding anniversary celebration and watched from the deck as the Boeing 747 Dreamlifter took off from Paine Field.

“This place brought us out here,” David King 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.”

If you go

Tickets for the Boeing Tour can be purchased online at www.futureofflight.org or by calling 1-800-464-1476 between 9 a.m. and 5 p.m. Monday through Friday and from 10 a.m. to 2 p.m. on weekends. A limited quantity of same-day, non-reserved tickets are sold onsite.