Pros
Job security, nearly impossible to get fired Very clear and defined roles Awesome projects and cool things you'll see Very remote friendly, unless the work is clearance required
Cons
Big company, easy to get lost in pointing fingers and red tape. You'll hear a lot of "well, _____ should know that, not me" or "this is how we've been doing it, so we'll keep doing it that way." Some may call this a pro, such that if you don't work well with some folks, you can just move, but that's easier said than done. Pay is just good enough that you can't really complain, but certainly lower end of competitive. Personally, I'm not a big fan of the majority of the money making products (aka, business decision drivers). Doesn't excite me as much as other new space ventures (SpaceX, Blue Origin, Virgin, RocketLab, Astra, etc). LM is not really a design engineering company, they are a design integration company. Not bashing integration, just saying that if you want to create from scratch, you're probably not in the right place.