Question: Looking for movie featuring Dragons vs. Navy (or Army, but the trailer featured battleship trying to shoot the dragons down).

Trailer also showed a dogfight between helicopters and dragons, capping (on the trailer) with a dragon setting a Blackhawk's blades on fire.

Answer: 
This sounds very like the British film [Reign of Fire](http://en.wikipedia.org/wiki/Reign_of_Fire_%28film%29), which included several scenes of fire-breathing dragons versus helicopters.

The trailer is [here](https://www.youtube.com/watch?v=Wg7bjwEXp7Y) and although there are various helicopter shots there's nothing specifically with the blades on fire.
MainStay Productions released a trailer on YouTube last year, about a movie project they are working on with BluFire Studios, ostensibly called Crimson Skies.
The premise is that a volcanic island erupts, releasing thousands of dragons from millenia-long slumber, that attack a small fleet of Navy vessels.

I checked on both MainStay and BluFire's websites, neither of which make any mention of the project, which makes me think that the trailer may simply be a "pitch demo" to try and find a studio willing to underwrite it. There is no other mention of the movie, other than the video, that I can find. 

Of course, this may also be just another elaborate YouTube hoax.