I've had an iFly for about a year now, and have never heard of "Naviextras", nor do I know why I'd want it. I did look up their website and see that they supposedly support the iFly, but again I don't know what data they provide that AP doesn't.
I also noticed that Naviextras has a support tab at the top of their website. I would guess that you would be better served by contacting them and asking for help with their product, rather than here.