A look at key events surrounding the Christmas Day attack on a U.S. airliner. Umar Farouk Abdulmutallab is accused of trying to detonate an explosive device hidden on his body as the plane approached Detroit on a flight from Amsterdam.
_June 12: Abdulmutallab applies for a visa at the U.S. Embassy in London.
_June 16: His visa is granted. The visa is a regular multiple-entry tourist visa valid until June 12, 2010.
_August 1-17: Abdulmutallab visits Houston, Texas.
_January: Abdulmutallab attends the University of Wollongong in Dubai.
_May 2009: Britain refuses to grant Abdulmutallab a student visa because the school on his application form was not a government-approved institution.
_August to early December: Abdulmutallab visits Yemen after receiving a visa to study Arabic in a school in Sana'a, according to the Yemeni Foreign Ministry.
_Nov. 19: Abdulmutallab's father goes to the U.S. embassy in Abuja, Nigeria, to express concern his son was in Yemen and had fallen under the influence of extremists.
_Nov. 20: The U.S. embassy sends a so-called "VISAS VIPER" cable with the information that Abdulmutallab's father had provided. The cable is sent to all U.S. diplomatic missions and the State Department in Washington, where it was also shared with the interagency National Counterterrorism Center for review.
_Nov. 20, 2009, Abdulmutallab's name is entered into the National Counterterrorism Center's Terrorist Identities Datamart Environment (TIDE) database based on information provided by his father.
_Dec. 16: Abdulmutallab's round-trip plane ticket is purchased in Accra, Ghana, for $2,831 in cash, presumably by Abdulmutallab himself, according to Nigerian officials.
_Dec. 24: Abdulmutallab re-enters Nigeria for only one day to board a flight from Lagos to Detroit, via Amsterdam.
_Dec. 25: Abdulmutallab allegedly tries to bring down Northwest Airlines Flight 253 as it approaches Detroit. The plane lands safely and he is taken to the University of Michigan Medical Center in Ann Arbor, Mich., for treatment of burns.
_Dec. 27: Abdulmutallab is transferred to a federal prison in Michigan.