My uncle died on nine eleven... he was the best pilot in Iraq.
Uncle's Unusual Demise
Explanation
Explain Bear
Okay, so basically this joke is funny because it mixes a really serious tragedy, 9/11, with a stereotype about people from Iraq being pilots, in a dark and twisted way. The joke implies the uncle was a bad pilot and involved in the terrorist attack. It's funny because it's so wrong, you dum-dum!