Signal-
From my understanding, which is severely limited, they can take months to get ahold of people's references. The amount of time it takes them to check with certain applicant's references can vary on a lot of things. It might be how long you said you needed to start work (I said 5 weeks). It might be what airplane they are staffing for now (I'm a Boeing guy I would assume). It could be by a ranking in the class by last name or how well you did.
Just the fact that some guys are 6-8 weeks out and still getting the call for a job tells me that their process has its own way of happening. Don't get discouraged or too anxious. I personally felt that my Panel interview was terrible and I was surprised they even called me back after my sim!
When did you interview exactly?