Here is the full list of all 52 Altitude achievements. It takes around 12-15 hours to unlock all of the achievements on Windows.
Shoot down 150 enemy planes
Shoot down 100 enemy planes
Shoot down 50 enemy planes
Shoot down 10 enemy planes without dying
Shoot down 4 enemy planes within 4 seconds of one another
Shoot down 3 enemy planes within 4 seconds of one another
Shoot down 6 enemy planes without dying
Shoot down 2 enemy planes within 4 seconds of one another
Shoot down 3 enemy planes without dying
Interrupt an enemy's afterburners with Loopy's EMP grenade. Easy peasy lemon squeezy.
Complete Training: Air Ball
Complete Training: Multiplanar Mayhem
Complete Training: Nuclear Launch Detected
Complete Training: We Fly High (Ballin)
Complete Training: Splanelunking
Complete Training: Pilot Certification