I was talking about this on another thread. I had my app accepted nine months ago. And just got email invite for the phone interview in august, then they rescheduled it for sept. One of my sources at NetJets told me that they are revamping their whole recruitment process, and because they are doing this, he said that they are going to wipe the slate clean this fall, meaning out of the 10,000 apps that they have on file, if you have not been called, you will have to re-apply.
Maybe this letter is part of that process. I'm not sure. All I know is that my contact said they would be kind of refreshing the system, which means people will have to resubmit there apps. For all I know, I probably should have recieved the same email you did since I was on file the same amount of time you were. It probably was a total crap shoot that I got offered an interview and you didn't. They probably drew straws. I would re-apply.