DETROIT -- A federal judge on Thursday sentenced a Nigerian man to life in prison for trying to blow up a U.S. airliner bound for Detroit on Christmas Day in 2009.

“This was an act of terrorism that cannot be quibbled with,” said U.S. District Judge Nancy Edmunds, who imposed the maximum sentence allowed.

A bomb hidden in the underwear of Umar Farouk Abdulmutallab, now 25, caused a fire but failed to explode on a Delta Airlines flight from Amsterdam carrying 289 people on December 25.

Abdulmutallab, who wore a white T-shirt and skull cap, sat impassively as the sentence was read out in a crowded Detroit court room.

Earlier, he used a four-minute address to the court to repeat that his attack was intended to avenge “the attacks of the United States on Muslims.”

“The jihadi is proud to kill in the name of God and that is exactly what God told us to do in the Koran,” said Abdulmutallab, who had pleaded guilty in October.

Edmunds said Abdulmutallab represented a threat to U.S. citizens and noted that he had not shown any remorse during two years in a federal prison in Milan, Michigan.

Prosecutors said Abdulmutallab had intended to bring down the jet over U.S. soil and was thwarted only by luck.

They showed a short video of the kind of blast that the powerful explosive known as PETN, which Abdulmutallab had hidden in his underwear, could have caused if it had detonated.

Several passengers who were on the flight told the judge they were still haunted by the attempted attack.

LeMare Mason, a Delta flight attendant who helped put out the fire caused by the bomb, said he was still suffering from night sweats and a dread of flying.

“I had a dream job of traveling the world and meeting all types of people. This man stole and robbed from me the pleasure. It’s punishment going to work now. It’s not a joy,” he told Edwards ahead of the sentencing.

Prosecutors last week offered new details about the plot, which they said was directed by U.S.-born Muslim cleric Anwar al-Awlaki, who had become an al Qaeda leader in Yemen.

Awlaki was killed in a drone attack in Yemen last September. In court papers, the FBI identified Awlaki as “chief of external operations” for al Qaeda’s Yemen branch as well as an Internet-savvy propagandist and recruiter.

When the bomb caused a fire but failed to explode, Abdulmutallab was quickly subdued by passengers and crew. The incident led U.S. officials to bolster airport security, deploying full-body scanners to try to detect explosives.