You need to go to mission editor, go to mission creator, then go through the list untill you find physical zone(i think its in system or something) make a new one, name it MYZONELOL or something. then go to mission inspector,select your zone, and find the field thats called Force applied(or something similar) and make it 0 0 1, or 0 0 10 or w/e suits your mood.
(its x y z, z is up, so 0 0 1 pushes you up)
You'll also have to modify its scale.