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take off, landing, calculating the weights... that stuff is more difficult but once in the air a kid could do what they did
That's right. It relly isn't hard to steer a plane in the air. Some even have. Driving a plane through the sky isn't that difficult, actually piloting it, well, that's not all that hard either but, you have to get a little training at least.
The hardest physical aspect of flying for most people to learn to do is land. Of course, these guys really didn't plan on thta anyway.
Just for educational purposes, go to the local airport where you live and see if they offer flying lessons. Tell the instructor that you just want to see how hard it really is. Some will take you up for the cost of fuel, some might take you up for free. You'll find out irst hand that there really isn't as much to it as people tend to think that there is.