Ok, so by far the best and easiest way to unlock this is once you obtain the Landscape tool (world 2 or 3, i can't recall off the top of my head), you need to stand in a open spot, take out the landscape tool, and change the size to as large as possible. Now continue to build upwards, what i found was 25 seconds of time spent building upwards equals 5 seconds of air time. Once you get a good height up, take the discovery tool out and choose from any vehicle you have discovered (I used the green bike), then drive off the edge and stay in the vehicle until you hit the ground. Achievement unlocked!