Still, Id really consider not going strait into multi.. linear should be fine, most people I know took it after calc 3, your allowed to take it after calc 2 if you want.
Ive considered going into aerospace but from what I know it is SUPER SUPER SUPER hard. Alot harder than mechanical or electrical which most consider to be somewhat hard... I bet you could still get a job with LM or Boeing as an electrical or mechanical, youd just might be limited on projects. Id personally love to work for Skunk Works...