Hi Greg,
I worked for the aerospace industry for 8 years after college (rocket launching from Cape Canaveral and Vandenburg, AFB). As far as I could tell, there was very little to no advantage to being an EIT or PE in that industry.
I've worked for a chemical company for 12 years since then, and still there seems to be very little advantage to being a PE. I think in general, there is little if any advantage to being a PE in large companies. If I had to put a number on it, I'd say there is a 10 to 20 % advantage, but most if not all of that advantage is in the fact that those people are generally more likely to work that much harder. It has little, if anything to do with the piece of paper.