They might not have seen the bird coming towards them. And I don't know about anyone else but if something unexpected touches me unexpectedly my first instinct is to get the **** away from me.

Wow. Your comment is straight up awful 70. I once had to go look something up on my computer in the middle of the night when I saw two glowing eyes staring at me in the dark. I ended up freaking out and nearly hit my black cat with my laptop. He wasn't happy with me for sure but sometimes animals do things we don't expect. OP is clearly trying very hard with his bird. More than I can say with a lot of bird owners.

70 does have a point... Most bird owners hear wings and automatically out their hand out as a landing spot--it is a pretty distinctive sound. And if just having a bird land on their hand surprises OP enough to smack the bird what are they going to do when the bird starts biting? The best way to stop a bird from biting is to not react at all--freak out like this over a bite and you've given a bird an idea for a new game that involves lots of blood. Plus you have to keep in mind birds are not domesticated animals--their instincts are much more survival oriented than those of a cat/dog. It can take them a long time to trust someone again. Some birds are more forgiving just like some people are but it can take a lot of blood and time to gain back trust from a bird. My hands are still scarred from trying to help an African grey who didn't trust people. And that mostly involved me sitting there with his beak through my thumb/fingers and talking quietly. Birds are not for the easily startled or faint of heart.

Not as awful as someone almost killing their bird when they have been training it to do exactly what it did. Logic dictates that if the bird was able to fly over to OP then they were doing something with the bird anyway be it getting food ready or something else, so then they should have known their was a chance the bird would fly out. Yet they were still jumpy enough to smack their bird across the room. So if you are that jumpy around your pet bird and almost kill it because of it, maybe owning a pet bird isn't for you.

Yes unexpectedly. This was not unexpectedly. The cage door was open meaning OP had opened and was doing something with the bird. So there should have been a level of expectedness that the bird could fly out, especially since OP had been trying to train it to do pretty much that. Yet when it does happen OP freaks out and smacks their bird across the room. Now say OPs family had opened the cage door and was doing something with the bird and then it flew at OP as he randomly walked in, then it's understandable they would freak out and whack the bird because it's completely unexpected. See the difference?