Officials are struggling to explain how a small aircraft could have crashed at Nashville International Airport yesterday morning without anyone noticing. It was six hours before a departing plane noticed the debris and let let the tower know they might want to take a look. Inside, they found the pilot and sole occupant of the plane, who apparently died on impact (his name is being withheld.) The plane itself was supposed to land in Ontario later that day, and how it got to Nashville remains a mystery. Right now, The National Transportation Safety Board is unsure if the pilot tried to communicate with anyone or sent out a distress call before his flight crashed …