I went through a hiring agency, but the interview process was the same. I had a phone inter view where they asked me about my resume and also finished off with several technical questions. After answering the questions correctly, I was offered to be scheduled an onsite interview. The interview onsite was about 3 hours long. It started out with a programming assignment and then a panel interview with about 6 engineers. The whole process took about 2.5 weeks

First: Phone screening in which I was asked to introduce myself, about my previous experiences, and some minor technical questions. Second: Actual interview in which I was asked more or less the same things that I was asked in the phone screening but in more detail and depth. Additionally, was assigned some C++ programming tasks with an aerospace theme to them. Be prepared to talk about past work experience and projects in depth. Third: More of a talk with an HR person discussing desired salary and preferred starting date. If you reach this point it's likely that you're already accepted from a technical standpoint.