Who uses Tableau doesn't matter as much as where and how they're using it. Broadly speaking, what types of reports are you looking for? Production floor workflow? QA/defect analysis? Number of days on the job without getting blown up? Customer support issue tracking? Inventory tracking/movement?
You'll find (at least pockets) of Tableau at most of aerospace / defense enterprises - data is data after all, and Tableau is one of the best tools to deal with it.
Here are a few that come immediately to mind for me (these are folks who have presented at customer conferences, been a part of case studies, or done other "public" stuff):
- Nasa (JPL)
Tableau has been in this space for a while - you certainly wouldn't be a pioneer (in this case, a good thing).