Cats are skilled at flipping over onto their feet during a fall, but you shouldn't rely on this behavior in all circumstances. Despite having physics and the evolution of a righting reflex on their side, cats can and do occasionally get injured during falls.
Physics and Falling
Cats have a righting reflex that causes them to flip feet-down whenever they start to fall. This reflex happens automatically, without any conscious thought on the part of your kitty. When it comes to falls from extremely high places, your cat is even more prepared. When a cat falls, she doesn't fall as fast as a larger animal or human would. The terminal velocity of a cat, or the maximum speed she reaches during a fall, is about 60 miles per hour, compared to about 120 miles per hour for a falling human. She also spreads her limbs out, similar to the way a flying squirrel does, to slow her descent. Once she reaches the ground, she lets her muscular legs take the shock of the landing so her vital organs and head stay protected.
One reason your kitty has such a useful ability is because she is essentially a climber and jumper at heart. If you've ever caught your pet on the kitchen counter, watched her navigate the edge of a fence or seen her scramble up a tree after a bird or squirrel, you're already familiar with her love of high places. Because cats naturally want to be in places where they can easily fall, they've evolved mechanisms to cope with the inevitable slip or stumble.
Some cats are so good at surviving falls that they can slip out of a skyscraper window and come out alive. So many cats have survived falls from high buildings that they've even gained a name for the phenomena: high-rise syndrome. A 2004 study in the " Journal of Feline Medicine and Surgery" found that, of 119 cats who fell from heights averaging four stories, more than 95 percent of the cats survived. However, about 46 percent of those cats had broken bones after their fall, and many others had internal injuries or external cuts and bruises.
While your cat is well-equipped to handle a fall, don't neglect her safety or assume you don't need to worry about her scaling heights. Keep upper-story windows securely closed when your cat is in the room, and don't presume that a screen will keep your kitty safe. Many cats have dived at a screen to catch a bug or in play only to have the screen pop out on them. If your cat is overweight or out of shape, even a fall from a short distance can be dangerous. Heavier cats may not be able to right themselves as quickly, so they may hit the ground before the righting reflex gets them flipped into a position to handle the fall.