Fulfil the required task to unlock the achievement, there are 18 in total.

Achievement	How to unlock
A little longer!	Hold terminal velocity for 30 seconds
Booster	Collect a boost crystal, which gives you a speed boost
Buzz the Village	Pass close to the tall tower in the village at high speed in Rift Valley
Crazy Fast	Reach terminal velocity
Entering Orbit	Hit 5km in altitude
Gold Rush	Get all the gold crystals
Handfull	Collect 25 crystals
High Altitude	Hit 1km in altitude
Hold on!	Hold terminal velocity for 10 seconds
Long flight	Fly continuously without landing or crashing for 5 minutes
Perfect Pink	Get all the pink crystals
Pocketfull	Collect 50 crystals
Sky High	Hit 3km in altitude
Surface Skimmer	Keep the altitude warning on for 60 seconds in Rift Valley
Take a Break!	Fly continuously without landing or crashing for 12 minutes
Trans Atlantic	Fly continuously without landing or crashing for 8 minutes
Volcano Crater	Fly into the crater of the volcano in Rift Valley
Waterfall	Try to fly into the base of the waterfall in Rift Valley