* Boring repetitive gameplay.
* Bad AI.
* Tiny maps.
* Awful quality of maps (ground textures are ugly, lack of objects).
* Graphics are not good (it may looks good on screenshots, but it ugly in motion) - trees and clouds are just plane sprites (reminds me of 2000th).
* Lack of achievements.
* No replay value.
* No simulator control scheme for gamepad.
* Dead and pointless multiplayer.
* Story. Your alter ego is muted. Why Thompson fight for so long? For what? There is no answer.
* Relatively long campaign.
* About 20 authentic planes and copters.
* You can control up to 6 various aircraft at single mission and switch them freely.
* Random rescure MIA pilots from your squad are interesting for first 1-2 times.
Some additional thoughts:
This game has somekind of historical accuracy: Americans are bad - bombing civilians, spreading agent orange, napalming villages. But if you don't like to be bad, you don't like to play this game. Well, if you American - you may like such "patriotism".
It is the worst game of the Air Conflicts series.
If you want to get flight arcade game look at HAWX1-2 (better graphics, better gameplay, better replay value) or Ace Combat (fun gameplay).
I think it is very mediocre - this game is surely not my best buy.
Metacritics score: ~44 (http://www.metacritic.com/game/pc/air-conflicts-vietnam)