By Kiran Khalid and Paul Cruickshank
New details about the final plans for the 2009 plot to take down an American jetliner on Christmas Day paint a vivid picture of the significant involvement of Anwar Al-Awlaki, the American-Yemeni militant cleric killed in a drone strike last September.
The information came to light Friday with the release of a Justice Department sentencing memo issued ahead of next week's sentencing of Umar Farouk AbdulMutallab.
AbdulMutallab's trial last year was cut dramatically short when he pleaded guilty to trying to detonate an explosive device in his underwear aboard a Christmas 2009 flight to Detroit.
The short duration of the trial had left many questions unanswered, most notably the role played in the plot by al-Awlaki.
After al-Awlaki's death, President Barack Obama emphasized al-Awlaki's operational role within al Qaeda in the Arabian Peninsula (AQAP), al Qaeda's affiliate in Yemen, labeling him the head of the group's external operations and stating he "directed the failed attempt" in the "underwear bomber" plot. Until now, details weren't well-defined.
In the sentencing memo, the government states that AbdulMutallab sought out al-Awlaki in Yemen in 2009. When he arrived there, the defendant visited several mosques and asked people if they knew how he could meet al-Awlaki according to the document. Eventually, he made contact.
"After receiving defendant's message, Awlaki sent defendant a response, telling him that Awlaki would find a way for defendant to become involved in jihad," the court documents say. "Thereafter, defendant was picked up and driven through the Yemeni desert."
Once AbdulMutallab met al-Awlaki, whose online sermons he had followed for several years, the two men discussed martyrdom and jihad for three days.
"Throughout, defendant expressed his willingness to become involved in any mission chosen for him, including martyrdom - and by the end of his stay, Awlaki had accepted defendant for a martyrdom mission," the memo states.
The memo reveals another new detail about how the wheels were set in motion. After leaving al-Awlaki's house, AbdulMutallab was introduced to AQAP's top bomb-maker, Ibrahim Hasan al-Asiri. Al-Asiri is a Saudi citizen who has developed a genius for bomb design, but remains a shadowy figure.
Before moving to Yemen four years ago, al-Asiri was part of an al Qaeda-affiliated cell in Saudi Arabia targeting oil facilities, according to U.S. authorities.
According to authorities, Al-Asiri designed the underwear bomb then instructed AbdulMutallab how to use it including "having defendant practice the manner in which the bomb would be detonated; that is, by pushing the plunger of a syringe, causing two chemicals to mix, and initiating a fire (which would then detonate the explosive)."
According to the government, al-Awlaki also instructed AbdulMutallab about his martyr video, arranging for a professional film crew to film it.
"Awlaki assisted defendant in writing his martyrdom statement, and it was filmed over a period of two to three days. The full video was approximately five minutes in length," says the Justice Department's memo.
In his short time under Awlaki's tutelage, AbdulMutallab who is the son of a Nigerian multimillionaire and was educated at elite schools and at a top London University, met many key al Qaeda operatives according to the memo.
The memo presented by the government also reveals for the first time that AbdulMutallab also interacted with Samir Khan, the former editor of AQAP's jihadist magazine called "Inspire." Khan was killed by a targeted drone attack along with al-Awlaki in September 2011.
The government's memo helps explain why senior Obama administration officials have contended that al-Awlaki was an orchestrator of terror plots, not just an inspiration to terror aspirants. The final pages of the sentencing memo intended to keep AbdulMutallab behind bars for life includes chilling details that illuminate that involvement.
"Awlaki instructed defendant that the only requirements were that the attack be on a U.S. airliner, and that the attack take place over U.S. soil ... Prior to defendant's departure from Yemen, Awlaki's last instructions to him were to wait until the airplane was over the United States and then to take the plane down."
CNN's Deb Feyerick and Nic Robertson contributed to this report.