A cat's whiskers can detect very minute air movements. Even without whiskers, a human face can feel slight puffs of air at tiny speeds, speeds that falling objects hit within inches. Wind alone should give the cat enough directional information within milliseconds. Whether it can adjust its body position in time is a different issue. It certainly knows in which direction it is falling practically instantly.

Cats also have memory. They remember in which direction gravity was pulling them before the fall. Absent every other sensation that memory should be enough to get the process going even absent new sensations.