I've never been a Top Gun fan but did hear they were trying some innovative stuff to improve the cockpit footage and that caught my interest. If they could just make this in IMAX and have Tom Cruise without dialogue flying F-18s through canyons for 60 minutes it might be great. That footage looks incredible and completely convincing(judging from the trailer).
That has to be real footage with the cameras hidden or speeded up no way its all VFX if it is then the detail is staggering next level work
I suspect either cockpit VFX replacement or some kind of fancy camera rig with a special zoom lense.
Cruise made a surprise showing at San Diego to premier the trailer and said they had developed camera that could be mounted and capture as much of the flying for real.So your hunch was accurate about the camera rigs.
I'm wondering though if maybe the vfx is, like you suggested, cockpit enhancement to make it look like Cruise is the main pilot when maybe he was merely the co-pilot? I do know he was a co-pilot in the original for some of the footage and maybe they took it a step further with the sequel and used the vfx advancements since and will rework the cockpits to move Cruise into the pilot position and paint out the real one.