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