Number one child flew at 4 1/2 alone in the back seat of the Cub.
Number two child at 2 1/2.
Number three child at 6.
It was all driven by the children concerned, although number two was pretty exceptional. Initially I took the stick out of the back, but stopped doing that quite quickly. They understand pretty quickly that if they muck about they risk dying, along with you. I think it's good for them to have that appreciation at an early age.