Here is the full list of all 28 Steam and Metal achievements.
10000 aircraft shotten.
Beat the game on hard.
Beat game with score one million or more!
Kill 30+ enemies with a single(!) air-torpedo.
Achieve shooting accuracy 77%
Achieve shooting accuracy 50%
Pass through level without kill anybody but boss.
Complete the game.
Beat level 5.
1337 aircraft shotten.
Destroy 300 aircraft in one level.
Destroy 69 aircraft continuously
Destroy 111 aircraft continuously
Beat level 4.
Take 1000+ bonuses on level.
Beat level 3.
666 aircraft shotten.
Achieve accuracy 25%
Level is beaten without a single scratch.
Beat level 2.
Accomplish level with rank A.
Destroy 200 aircraft in one level.
Accomplish level with rank F.
Beat level 1.
Level beaten without air-torpedos.
Accomplish level without lossing a single life.
Destroy 100 aircraft in one level.
Destroy 24 aircraft continuously