For this achievement you must get a total of 150 seconds of air time in one event and win that event. This does not mean 150 seconds in the air at one time, that would be impossible. This can probably be pulled off in a World Tour Race event. But, if you want to make it easier on yourself just set up a Single Race event of five or more laps, that way you have more time to get more air and more time to catch up to the front runners if you fall behind. Although Pure's online community isn't that active, if you want this achievement bad enough you will wait for the people to join.