Here is the full list of all 29 Airhead achievements.
Use an air cylinder without holding Head.
Leave Head behind while you go for a swim in the large lake.
Opened every shortcut.
Return to the start of the game.
Reach the lowest point in the world.
Get all library entries
Collect every eye in the game.
Collect every ear in the game.
What is the purpose of this odd object?
With all pieces found, it is up to you to piece them together.
Activate your first machine.
Light up the darkness.
Use air to jump higher than ever before.
Dive underwater whith an inflated Head.
Take direct control of a machine.
Break your first window.
Fully upgrade Head.
Find Head.
You filled the larva with air, making friends with an Airhunter.
You made your way into the facility.
You used the tram to get across the abyss.
You got your hands on a new head.
You defeated the Collector and the Constructor.
Got thrown off the roof.
You freed the Airhunter, making one more friend.
Head is safe, but at what cost?
You restarted P.A.I.C., giving the world a second chance.
You opened the gate and left P.A.I.C. and Head behind.
Save Head within 2 hours.