Nigerian tries to blow up Delta Flight 253 in Detroit

Abdul Farouk Umar Abdulmutallab, a 23-year-old son Nigerian national, attempted to ignite an explosive device aboard Delta Airlines Flight 253 from Amsterdam to Detroit, Michigan. Abdulmutallab is the son of the former chairman of the First Bank of Nigeria, Abdul Farouk Umar Abdulmutallab. According to stories in both the Detroit News and This Day, the father had repeatedly warned authorities about his son's radical leanings going back more than two years. The younger Abdulmutallab claims to have received both his incendiary device and training on how to use it from Al Qaeda forces in Yemen. Why was he allowed to board a flight bound for the United States?