What might the kite flying tournament symbolize?
The kite flying tournament in Chapter 7 is one of the most significant episodes in the novel, as it accurately shows the relationship between Amir and Hassan. Before the tournament, Amir is nervous and briefly considers pulling out of the tournament. However, Hassan encourages him, and Amir ultimately wins the tournament. In this chapter, we see Hassan's unwavering love for and commitment to Amir; Hassan takes the blue kite to run it in celebration for Amir, saying, "For you a thousand times over!"
Unfortunately, the incident that accompanies the kite tournament is one that is also telling about the relationship between Amir and Hassan. As Hassan is raped by Assef, Amir watches, unable to act in Hassan's defense. Hassan returns, later, with the blue kite still in hand; although Amir almost apologizes, he does not. Neither mentions the incident again (most specifically, Hassan, who knows Amir was there, never questions Amir's decision not to act.) Amir, stricken with guilt, eventually tells a lie that drives Hassan and Ali from Baba's house so that Hassan's presence won't be a daily reminder of the situation to Amir.
Ultimately, the novel ends with a kite-flying scene between Amir and Sohrab which symbolizes a sort of repair in the relationship between Amir and Hassan. Even though Hassan is dead, Amir, through persistence and patience, is able to finally elicit a smile from Hassan's son.