A really good game IMO with lots of quality content in. I like the music, the artwork and the depth in the attack patterns for some enemies, especially for the bosses. They are really advanced, different and fun.
It is pretty inspiring. The game is a really nice try but there are some major bugs which I guess have given this game a low score. Most notably the cut-off enemy spawn for some levels. Sometimes when you start a level you only encounter enemies to the very left so most of them spawn off screen I guess.
I guess this game has been hard to code and given that most of the games here on Newgrounds are made by hobbyist game developers who are not very experienced I think it is a really nice try. Some tips tho: The game could use a tracking of how far you have got in each stage. The later stages can get tedious and you can get to a point when you question if it ever ends. The two types of shots were a nice feature I have not seen implemented in this way earlier. The waves that clear bullets were a little OP tho, but the projectiles that can not be cleared were a clever implemention. It forces you to use forks to hit the enemies.
The genre is wrong by the way. Horizontal Flight is when it scrolls to the side. This is vertically.