As a private pilot (which, admittedly, is a very different environment) if I had kids on board, then if at all possible they got to sit up front and fly the plane as much as they wanted and could. I've had kids as young as five fly the plane (while sitting on a stack of telephone books so that they could see out the windshield). It was always amazing how good even kids that young could get in just a few minutes at the simple stuff such as slow turns to a heading or gradual ascents and descents to a new altitude. I've had ten-year-olds do well enough that I was actually able to have them do straight-ahead stalls, both power-on and power-off, successfully. The basics of flying an airplane are actually incredibly easy to learn and perform and, in many ways, the bigger the airplane, the easier they are. It's all the other stuff that goes along with managing the airplane that requires the education, training, and experience and, there, the bigger the airplane, the more involved it becomes.Kids in the cockpit, what could go wrong?

