It sounds like you are getting "invited" to take the online psych assessment. If it's still like the one I took, it's several online pages of questions about various situations and how you perceive yourself. Nothing to be worried about. In fact, my interview sim partner said that his wife, a psychologist, actually looked over the test and said that it appeared that NetJets is simply trying to weed out sociopaths.
So if you don't have that problem, the test should only be about 10 minutes of your time on the road to an actual in-person interview.