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