Getting a PhD after two masters? So I am an undergraduate in university right now studying applied physics with applications in aeronautical/aerospace engineering. I have a 5th year M.S option to get my masters in physics with applications in a certain field. After that 5th year M.S I want to go and get my masters in aeronautical/aerospace engineering but always wanted to do research at the PhD level, so is it possible for me to get a PhD in physics or aerospace/aeronautical engineering after two MS's in physics and aeronautical engineering respectively?
If you can afford to do all that graduate study without a TA-ship or RA-ship, more power to you!  Perhaps you could get the two masters concurrently... or at least get some of the coursework for the aeronautical/aerospace engineering masters out of the way.  Maybe there will be some nice overlap that will speed things up a bit for you.

You could also take those a/a courses in the early stages of a PhD program in either field.