By Paul Reynolds
World affairs correspondent, BBC News website
President Barack Obama's explanation of the security failure over the alleged "jet bomber" Umar Farouk Abdulmutallab indicates that this was more than a case of someone not joining up the dots.
He used the word "systemic" to describe the failure.
Something in the system did not make it easy for those dots to be joined.
The weak point appears to be in the system under which a suspect's name is moved onto vital watch lists - or not.
The president focused on the warning given by the alleged bomber's father to the US embassy in Nigeria that his son was a potential threat and had gone to Yemen, a known recruiting and training ground for al-Qaeda.
President Obama said: "It now appears that, weeks ago, this information was passed to a component of our intelligence community but was not effectively distributed so as to get the suspect's name on a no-fly list... had this critical information been shared... the suspect would have never been allowed to board that plane for America."
Umar Farouk Abdulmutallab has been charged over the incident
The father's warning was passed on by the US Department of State on 20 November, spokesman Ian Kelly was reported by the Associated Press as saying.
It went not only to all US diplomatic missions and to the State Department in Washington but also to the US National Counterterrorism Center (NCTC), which collates and considers all such information.
However two things did not happen.
The first was that Mr Abdulmutallab's existing tourist visa, allowing him to enter the United States, was not revoked.
This gave him multiple entry rights for two years from June 2008.
The second was that his name was not put on the vital watch lists that are an essential element of the systems designed, post-9/11, to prevent suspects from entering the US, like the 9/11 hijackers did.
In addition there are reports in the US media that US intelligence picked up suggestions that a Nigerian was being prepared in Yemen for a terrorist attack. If so, this made little impression.
Instead, his name made it only onto a database known as Tide - the Terrorist Identities Datamart Environment.
The NCTC website describes its basic function: "The
database includes... all information the US government possesses related to the identity of individuals known or appropriately suspected to be or have been involved in activities constituting, in preparation for, in aid of, or related to terrorism..."
Every day this list is reviewed and every evening analysts send a subset of data to the FBI's
Terrorist Screening Center (TSC)
for use in a watch-list.
This watch list is the basis for which people are either subject to further questioning and checking before they fly or are banned from flying to the US.
As of January 2009, there were more than 564,000 names in Tide.
Of these, some 14,000 are reported to be on the screening list and 4,000 on the no-fly list.
The problem in this case was that Mr Abdulmutallab was never transferred from Tide to the watch lists.
It seems that the information from his father was not enough to trigger that move.
That might have been the critical systemic failure alluded to by President Obama.
But why not?
Chad Kolton, a spokesman for the FBI's TSC, is reported by CNN to have said that there was not enough hard evidence to back up Mr Abdulmutallab's father's fears.
The FBI itself states that "only individuals who are known or reasonably suspected to be or have been engaged in conduct constituting, in preparation for, in aid of, or related to terrorism are included."
Security has been stepped up at airports across the world
So it seems that something more than a father's fears was needed, even though the Yemen connection should, to say the least, have raised a red flag.
Yemen is not a new front in the war against al-Qaeda.
A well-known trail leads to and from regional al-Qaeda leaders there.
One systemic reform is likely to be, therefore, a loosening of the criteria under which someone can be moved from Tide to the screening list.
Another is that US visas will be even harder to get and will be subject to review if new information comes in.
Before 9/11, visas for the US were easy to obtain.
Since then, and also since Richard Reid the British shoe-bomber tried to ignite explosives in his shoe-heel not long afterwards, the procedure has been tightened up. A face to face interview at least became necessary. While waiting for such an interview (my first) at the US embassy in London I joined members of a London orchestra who were also about to be quizzed.
There has been a comment in the US that the country should have known about Britain's refusal to give another visa to Mr Abdulmutallab (he had been to London before and studied at University College London).
However that refusal was not because of him but because this time he applied to a bogus academic college.
So under US rules it might not have been regarded as security-significant.
The question of profiling passengers has already been raised as well.
The Israeli airliner El Al has been doing it for years.
Britain refused to give Mr Abdulmutallab a visa a second time
Anyone flying on El Al knows they will be questioned and checked, sometimes several times, before they can board.
They and their luggage are subject to close scrutiny.
Some rather primitive methods of profiling have been tried in the US and the UK.
One of these involves monitoring passengers in case they show signs of unease or distress.
However, al-Qaeda was aware that hijackers and bombers might give themselves away a long time ago.
After 9/11, instructions were found that told the hijackers to smile and appear relaxed on the way to and in the airport, and on the plane.
In Mr Abdulmutallab's case, the reports are that he sought to reassure passengers around him when he started to fiddle around under a blanket, by saying that he felt unwell.
One further reform might be the use of body-scanning devices.
The Dutch authorities have already announced that these will be used for all flights to the US. The Nigerian authorities have followed suit. Others might follow.