<p>Besides the issues you have identified around security and clearance, aerospace/aeronautical engineering tends not to be terribly scalable. That is, you are really looking at a few key (but really awesome) employers in the field. </p>
<p>I think similar (but different) analysis could be found in say structural engineering (where wind dynamics/deflection) are hugely important and yet employment in structural engineering is quite ubiquitous. That is, each major city will have many top structural engineering firms whereas aerospace/aeronautics will be limited to certain areas. I agree though that aerospace engineering is really cool and fasicinating (and wildly difficult as well). </p>