Very subtle whip maneuvers can be initiated (while still in mid-air) to optimize the bike's landing angle for touchdown. Sometimes you won't even know your next line until you are in mid-air and can actually see it suddenly appear. Objects like small boulders in your favorite rut can make you decide to change your line once you are airborne and can now see it.  Also a rider in front of you may have suddenly grabbed the exit rut you had planned on using and it now looks like its going to take him "all year to get through it".  The ability to alter the bikes angle in mid air now becomes very important for landing in exactly the right direction and under full power the moment of touchdown.  This is particularly effective if its combined with a front wheel landing (and the back wheel just slightly offset) causing the whole bike to be in the perfect position to resume your drive.