There will be no actual flying on planes. Maybe(just maybe) a chopper. Consider this - you are facing a skyscraper that has all sorts of levels and details inside of it. A possible way to be to bring a chopper down to that building's LZ on top of it and then go down from the top. That would be awesome and people would not have the need to go all the way by elevator (even if the cutscene for that is skippable)

But no, other than that idea, no flying whatsoever except for certain story-related or side-quest related cases