His death and their intent
I believe Bobby was real, and it was obvious to me even as a kid that his flying away was a metaphor for his death. I had assumed that the radio flyer crashed and he died from the fall, but in revisiting the movie, I think it's more likely that he was beaten to death by the King. How do you think Bobby died? Even if the King didn't kill him, he would have died anyway in the inevitable crash. Which leads me to another question:
Did the boys know deep down that Bobby would probably die in his escape, making it sort of a subconscious suicide? Were they fully aware of it, making it completely a suicidey? Or did they truly believe in their childhood innocence that Bobby would be able to fly? I'm leaning toward subconscious suicide, or intended subconcious suicide if Bobby was murdered. They believed in the fantasy, but in the back of their minds knew how it would likely end. What are your thoughts?