As I just started at Boeing, working on contract for Dell, this is true. Not everyone is off, as contract employees don't get the Holiday, and they do a lot of network upgrades as well, but for the most part, Boeing turns into a ghost town which is really weird.
I'm a month into my Network Tech job at Boeing, and the new and shiny has worn off. I still enjoy it, but the corporate BS and red tape is starting to shine through, and the job is pretty repetitive. I'm getting great experience though, as this is my first networking job, and when things go wrong, because the Cisco IOS config we received from the designers is wrong, we sometimes have to troubleshoot, and that experience is invaluable.
I'm working 3rd shift, 11pm-7:30am, and some nights we are done by 2am, and sit there until time to go home. There are so many approvals things have to go through in order to take the network down for anything that when done with a job for the night, we are done, regardless of how long it took.