Victor, this is a very informative site for someone who may be looking to get a cockatoo: http://animal-world.com/encyclo/birds/co...rofile.htm
In the article it recommends that the cage for any bird should be "at least 3 flight wingspans" for a comfortable fit. They should get exercise outside their cage, as well. The bars should be horizontal for climbing. It also warns that a cockatoo's beak strength can pop joints on the cage and bend the bars, and you should get a good snap lock.
Any bird can fly, but bird owners often keep their bird's wings clipped to prevent their flying too easily. Many accidents have happened with pet birds flying into windows and door walls, sometimes resulting in death by a broken neck. I don't clip either of my birds wings though. My Quaker hovers like a helicopter. The Eclectus rarely flys, but sometimes he does crash into things. He's very clumsy and not a skilled flyer. I don't really worry about him flying because he never gets up any speed to do any damage to himself.
dashboard, I would love to see a hummingbird freely flying around a friend's house! That would be super cool!