Minh Pham, 33, broke down in tears after expressing regret in a New York courtroom and recognizing the severity of his punishment in America five months after pleading guilty to terrorism charges.
A Muslim convert who left Vietnam as a baby and spent most of his life in Britain, Pham travelled to Yemen in December 2010 to receive military training from Al-Qaeda in the Arabian Peninsula (AQAP), a group that has claimed repeated attacks on the West.
He returned to Britain, where he had left behind his 8-months-pregnant wife, in July 2011 after offering to carry out a suicide attack and being instructed to bomb civilians arriving at London's busiest airport from Israel or America, the court heard.
"I made a very serious mistake," Pham told Judge Alison Nathan before choking up at the prospect of spending decades in a maximum-security American jail separated from his family.
Dressed in navy prison scrubs, an orange T-shirt and orange canvas shoes, he denied that he had ever intended to hurt anyone, saying he had promised to carry out the attack only to get home.
"I do regret it," he said. "I'm not used to the American system and the severity of the sentence," he added before wiping away a tear.
Nathan said Pham had been convicted of some of the most serious crimes in the country, calling the details "extremely disturbing" and describing as horrific his instructions to tape bolts around the bomb he was supposed to detonate at Heathrow's arrivals' hall.
"Mr. Pham was a trusted, skilled and for a time, a dedicated participant of AQAP 'who agreed to carry out' a horrific and violent suicide bombing," she said.
The British authorities stopped him on his return from Yemen. He had a Kalashnikov bullet in his luggage and money from Al-Qaeda to rent a home to build the bomb, but was subsequently released on bail. Re-arrested in June 2012, he was extradited to America last year.
Renounce terrorism
Pham pleaded guilty in January to providing material support to AQAP, conspiring to receive military training and using a machine gun.
Anwar al-Awlaki, a U.S.-born AQAP leader killed in a U.S. drone strike in 2011, instructed him how to build a bomb, which he was to hide in a backpack in order to attack London's busiest airport, prosecutors said.
The U.S. government had requested the maximum sentence of 50 years, the defense 30 years.
Nathan said she imposed a sentence below the maximum because Pham had renounced terrorism, condemned Al-Qaeda's 9/11 attacks and expressed regret for distorting Islam.
But prosecutors told the court that Pham exhibited unwavering commitment to AQAP, saying his expressions of remorse were not believable after he lied repeatedly to his wife and the British authorities.
They said he used his fluent English and graphic design skills to work for Inspire, the group's magazine read by extremists in the West, including the brothers behind the 2013 Boston Marathon bombing.
There was no sign he had cut ties with Al-Qaeda, prosecutors said, adding that he had every intention of carrying out the attack one day.
Pham's lawyer Bobbi Sternheim said the defendant was the terror group's perfect target, with his slight frame and unassuming face. "He's certainly not the picture of Al-Qaeda."
"The court should sentence him for what he did, not for what the government thought he was going to do," she said.
Formed in 2009, AQAP has been linked to a string of attacks, including the Charlie Hebdo massacre in Paris in 2015 and an attempt to blow up an American airliner over Michigan on Christmas Day in 2009.