A very long time ago. They let me fly the 747 sim. The better visit was to their surplus store, where I got my trusty Cleco gun.
Did they tell you how many days it took to go from start to finish?I managed a VIP tour of the Everett wide body assembly line back in 1999. In the one end of the incredibly massive building they start assembly from scratch, by the time it reaches the other end it is a complete aircraft. Truly amazing!
I believe weekday tours are still available