He removed his shoes, passed through the metal detectors and, with a ticket bought with cash in Ghana a few days before, Umar Farouk Abdulmutallab boarded his flight on Christmas Eve from Lagos to Detroit via Amsterdam with no further ado.
What happened shortly before his arrival in the US on Christmas Day we all know: flames and smoke but no full detonation. Disaster averted, if only barely.
His passage through security screening was one of several new details of his deadly odyssey that surfaced yesterday, courtesy of the authorities in Nigeria, who are anxious to shed any blame for the incident. "The security agencies did all that was required under the law to ensure that Nigeria complied with international standards," that country's Attorney General, Michael Aondoakaa, told reporters in Abuja.
But we also learned something else more shocking, further illuminating the extent of America's intelligence "screw-up", as President Barack Obama put it. It now appears that the analysts whose job it is to cross-reference the names of passengers arriving in the US from overseas with terror watch-lists realised there was something possibly not right with the passenger in seat 19A when he was in the air over the Atlantic. But there was not much to be done at that point – except to question him upon landing.
When the plane did land, of course – the worst of all outcomes having been prevented in part by the bravery of the crew and other passengers – officials had more to do than ask questions. They arrested him at once.
The task of mortified intelligence experts now is to trace more fully the suspect's steps in the days, weeks and months before he boarded the plane in Lagos, a journey into darkness that took him from London to his native Nigeria and from there to Yemen, Ethiopia and Ghana.
A version of those travels was offered yesterday by a Deputy Prime Minister of Yemen, Rashad al-Alimi. It accords in part with what officials have already gleaned, in part from information offered by the suspect himself. Most importantly, the plot itself does appear to have been hatched during meetings in Yemen between Abdulmutallab and operatives linked to al-Qa'ida.
Moreover, officials in Yemen concede that among the people the suspect may have met in Yemen is Anwar al-Awlaki, the radical American Muslim cleric who was already very much on the radar of the CIA and the FBI because of emails he exchanged with Major Nidal Malik Hasan, the US Army psychiatrist behind the Fort Hood massacre on 5 November. Here too is another area where US intelligence seemingly failed to "connect the dots", to use President Obama's phrase.
But the Yemeni government, which is also anxious to minimise the damage to its standing, stressed that the explosive device did not come from Yemen but instead from Nigeria. That may be a stretch, if indeed he was in Lagos airport for only 30 minutes, as officials there contend.
Officials in Yemen believe that Abdulmutallab arrived in the country in August 2009. They say that he was driven to the airport to leave the country on 21 September but that he then disappeared.
It is after that date that he is believed to have met "al-Qa'ida elements" to agree details of the Christmas plot. All the details appear to have been agreed by 4 December, when he allegedly departed Yemen, en route to Ghana, where he bought his plane tickets.
All in all, quick work to set up a suicide mission that almost triggered the worst terror attack in America since 9/11. Yet all those weeks – from 21 September until 24 December, it would seem – offered clue after clue that something very bad was afoot. But, as US officials point out, it's easier to see them in hindsight.