I've spent my entire career as an engineer in both the aerospace and defense sector with a short detour in nuclear power.
You can enter the sector either as a technician (no degree required) or as an engineer (degree required).
Most large defense contractors will reimburse you for any costs you incur while pursuing an advanced degree.
I would recommend a masters but not a PHD. PHD's are a waste of time unless you want to teach at the University or do pure research. Hands on experience in design, devlopment, testing and production is were the action is. To work in this area as a MTS (Member Technical Staff) requires a BS in engineering as a minimum.
Defense contractors put a premium on ex military technicians as well as engineers. If you put ex military in your resume, especially if you have experience with a weapon system that the company is currently manufacturing and maintaing you are almost guaranteed a job.
At my company ex-submariners (both enlisted and officers) were common. Many of the ex-Navy officers were graduates of Annapolis.
There are also many good careers working for the Dept of Defense as a federal employee. The government has a multitude of aeropspace/defense testing and research facilities throughout the US. Just think; Rumsfeld could be your boss. ;^).
Yup, I found that defense contractors gave far better educational benefits.
I work for a civilian products division of a major corporation which is primarily known for defense aerospace work. So I get those nice educational benefits and am able to transfer to one of the aerospace divisions whenever I'd like. ;-)
I'm working on my master's...don't want to take a leave of absence from work to get a doctorate. My company pays 100% of all tuition and expenses. Not a bad deal, not at all!
PhD or not, students who are foreign nationals just don't have the same sort of opportunities with defense contractors. Heck, my civilian division doesn't like hiring foreign nationals. Why deal with visas and green cards when there are qualified American engineers to be hired?