"cgi or "real" aircraft?"
Good question. Unfortunately the answer is "both".
Being a fan of the genre myself, I'd love nothing better than to see it all done with real aircraft or replicas (Waldo Pepper), but given the number of dogfights, damaged aircraft, and crash sequences, the use of real aircraft for the entire project would be difficult, cost-prohibitive and dangerous. Good news is, the CGI company is also fans of military aviation. I can't say too much, but rest assured we've discussed making the scenes as gritty and realistic as possible where CGI is required. In short...we want you to get white-knuckled watching it, because it's what we want too.
As for correct Mk's, every effort will be made to get that right as well. Keep in mind though, budget and aircraft availability will be a factor here.