So above it all (20G)

Spend at least 25 consecutive seconds in the air (helicopters don't count).

This can be done once you have 3-4 points in the "Movement" tree. First start off by jumping off the highest building you can find (See Icarus) and once airborne hold . Once you notice your Heller start to fall hold and continue your glide. You should be able to repeat this 2-3 times before having to go into a free fall.

Note: If you touch anything at all (even enemies) the timer will reset.