Actually, the only way to ensure that your cat does not land on its feet is to drop it from a very small distance. Cats are very good at flipping around to get their feet under them when dropped. In my experience, dropping a cat (upside down) from a distance of about 12 inches off the ground will be enough for the cat to rotate 180° before hitting the ground. If you were to drop a cat from say, 1000 ft, it would flip around until it was falling feet first and then continue to fall the next 999 feet in this position.

Cats can survive falls from very high places (there is record of one cat who fell from 32 floors up and survived with only minor injuries). Interestingly enough, past a certain point, the chances of the cat getting seriously injured actually decrease. This is related to the concept of "terminal velocity":

vt = [(2mg)/(CρA)] ½

vt represents the terminal velocity.
mg is the mass of the falling object times the earth's gravitational pull (g = 9.81 N*M/s2).
C is the drag coefficient (a variable related to air resistance)
ρ is the air density
A is the effective cross-sectional area that will be experiencing the resistance from the air.

Once an object falling through vertical space toward the earth reaches a certain speed, it will cease to accelerate, and will continue falling at this constant rate. A falling cat, sensing the fact that it is accelerating toward the earth tucks in its head and bends its spine in an upside down "u" shape. Once our feline friend reaches its terminal velocity, it will cease to accelerate and will begin to relax, stretching out its legs, neck and spine into a more horizontal position. This action significantly increases A the effective cross sectional area, and the cat slows until it reaches a new, lesser terminal velocity. As our feline friend nears the ground, she once again pulls herself into her instinctive landing posision in anticipation of the impact.

The reduction in speed resulting from the cat relaxing and spreading out is enough to actually improve her chances of surviving the incident.