So,my last thread didnt had eough informations,so here again,with turbulences i meant,like that the planes/helikopter are affected by wind and sort of holes in the air,and get a more realistic feeling,(i googeled arround and saw it in GTA5,there are turbulences too,so basically that the planes/helikopter can suddenly sink down a bit,or get affected by wind like they get pushed a little bit into the direction from wehre the wind comes(only if the wind is strong enough),or a vortex wich the plane is having,thats the reason why other planes crush if they fly close behind each other,such stuff.

http://en.wikipedia.org/wiki/Turbulence