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: 
Sounds similar to [Dragon Wars : D-War](https://en.wikipedia.org/wiki/D-War), although I haven't found a specific trailer (of which there are quite a few) with a Blackhawk's blades on fire. Plenty of dragons destroying helicopters in other ways though. Here is a [short trailer](http://www.imdb.com/video/screenplay/vi3466789145), and here is a [longer trailer](https://www.youtube.com/watch?v=YnQXvQ1R4gg). Some of the dialogue in the longer trailer is Korean, but the movie itself is mostly in English.

![Dragon-vs-copter](https://i.stack.imgur.com/Gk9s1.png)
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.