The problem is that even if the kid had started joking around over the radio, the pilot is forced to do exactly what he says. Besides, it's not like the father who was sitting right next to him could do anything at all. What was he gonna do? Overpower a child? That's impossible. He couldn't have radioed the plane again either, since the signal terminates after the pilot's gotten his orders, so basically all the passengers survived solely because the kid didn't say anything stupid like "crash into a building".