A look at key events surrounding the Dec. 25 Christmas Day attack on a U.S. airliner. Nigerian 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.
2004 to 2005:
_Abdulmutallab is in Yemen for a year, learning Arabic at the Sana'a Institute of Arabic Languages.
_Abdulmutallab graduates from the British School of Lome in Togo. The month is unclear.
_He begins attending University College London in September.
_Abdulmutallab graduates from University College London in June.
_He applies for a visa at the U.S. Embassy in London.
_His visa is granted. The visa is a regular multiple-entry tourist visa valid until June 12, 2010.
_Abdulmutallab visits Houston.
January to about July:
_Abdulmutallab attends the University of Wollongong in Dubai.
_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 at a school in Sana'a, according to the Yemeni Foreign Ministry. He spends at least part of the time studying Arabic, investigators say. Students and administrators have described him as friendly and outgoing, with no overtly extremist views. Yemeni authorities are looking into Abdulmutallab's frequent visits to a mosque in the old, historic part of the city and the people he was with during his stay.
_A man tries to board a commercial airliner in Mogadishu, Somalia, carrying powdered chemicals, liquid and a syringe that could have caused an explosion. The case bears similarities to the plot to blow up the Detroit-bound airliner. The Somali man _ whose name has not yet been released _ was arrested by African Union peacekeeping troops before the Daallo Airlines flight took off. It had been scheduled to travel from Mogadishu to the northern Somali city of Hargeisa, then to Djibouti and Dubai.
_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.
_The embassy in Abuja 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.
_Abdulmutallab's name is entered into the National Counterterrorism Center's Terrorist Identities Datamart Environment (TIDE) database based on information provided by his father.
_The FBI and the Homeland Security Department issued an intelligence note about the threat picture for the holiday season. Officials say they have no specific information about attack plans by al-Qaida or other terrorist groups.
_Abdulmutallab's round-trip plane ticket is purchased in Accra, Ghana, for $2,831 in cash, presumably by Abdulmutallab himself, according to Nigerian officials. The Ghana KLM office shows that the ticket for his flight was bought at the Accra International Airport at about 8:00 p.m.
_In an assessment to law enforcement officials across the U.S., the FBI and Homeland Security Department say they have no specific credible intelligence indicating there are plans from al-Qaida or any other terrorist groups to attack the U.S. during the holiday season. The officials warn that al-Qaida and other terror groups "continue to seek innovative ways to conduct attacks and circumvent security procedures."
_Abdulmutallab re-enters Nigeria for only one day to board a flight from Lagos to Detroit, via Amsterdam. He walks into Lagos' Murtala Muhammed International Airport. Drawing no undue attention to himself, he checks into his flight to Amsterdam at 8:35 p.m. _ a little more than two hours before takeoff. He checks no luggage and carries only a shoulder bag, as he makes his way through an aging terminal decorated with red and green holiday bunting.
_Abdulmutallab is accused of trying to bring down Northwest Airlines Flight 253 as it approaches Detroit. Passengers hear a pop and see smoke. They rush Abdulmutallab and take him to first class where he is stripped in a search for explosives. He is silent and does not resist. The plane, carrying nearly 300 people, lands safely. Abdulmutallab is taken to the University of Michigan Medical Center in Ann Arbor, Mich., for treatment of burns.
_Abdulmutallab appears before a federal judge at the medical center. U.S. District Judge Paul Borman tells him that he is charged with trying to blow up the Northwest Airlines plane. Borman asks Abdulmutallab if he understands the charges against him. He responds in English: "Yes, I do."
_Abdulmutallab is transferred to a federal prison in Milan, Michigan, south of Detroit.
_President Barack Obama orders separate reviews of the U.S. terrorist watch list system and of air travel screening procedures.
_Al-Qaida in the Arabian Peninsula claims responsibility for the failed bombing, saying the attack was retaliation for a U.S. operation against the group in Yemen. The claim of responsibility was dated Dec. 26, but was posted on a Web site on the 28th.
_Preliminary findings from the Obama-ordered security reviews are due to the administration.