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