The clues piled up, but why did US security fail to act over terrorist?

Inquiry into how a Nigerian almost blew up a US plane despite warnings is due to report to the President today

America's much-criticised intelligence agencies were back under the microscope yesterday, as an urgent inquiry ordered by President Barack Obama got under way into how they failed to prevent the Nigerian student Umar Farouk Abdulmutallab from almost blowing up a US airliner on Christmas Day.

New details make clear that the authorities had unusually abundant clues that such a terrorist attack was imminent: not only the father's warning to the CIA in November that his son had developed alarming extremist Islamic views, but also intercepted "chatter" from al-Qa'ida leaders in Yemen about "a Nigerian" who was being trained for a terrorist operation.

Yet Abdulmutallab, 23, was only placed on a register of 550,000 people who might have links to terrorism, not on a smaller list of 14,000 subject to special screening before being permitted to board a plane, or on a 4,000 person no-fly list. Nor was his multiple-entry visa to the US revoked.

The focus is not just on the CIA, still smarting from its intelligence failures over the September 2001 attacks and Iraq's non-existent weapons of mass destruction, and which appears not to have passed on the information about Abdulmutallab. Fingers are also being pointed at the new agencies set to correct the shortcomings laid bare eight years ago – above all the National Counter-Terrorism Center (NCTC), supposed to serve as a clearing house for all terrorism intelligence.

Intelligence officials say their critics are merely indulging in the wisdom of hindsight and that no single piece of evidence against Abdulmutallab was conclusive. But the NCTC has reportedly complained that neither the CIA nor the National Security Agency, the US government's worldwide electronic eavesdropping body, made available all the data in their possession.

Dennis Blair, who as Director of National Intelligence is in overall charge of the 16 US intelligence-gathering agencies, told The Wall Street Journal that although improvements had been made since 9/11, "gaps remain and they must be fixed".

His words are acknowledgement of the similarities between today and eight years ago, when bureaucratic rivalries between the CIA and the FBI prevented the pooling of information that might have thwarted the terrorist attacks on New York and Washington. Something similar appears to have happened this time, prompting the thinly veiled anger of Mr Obama on Tuesday as he ordered a preliminary investigation into what happened to be completed within 48 hours, in other words today.

But Mr Obama was also trying to stave off political damage. Republicans are using the incident to make their familiar argument that Democrats are weak on national security. In particular, they have seized on the remark by Janet Napolitano, Secretary for Homeland Security, that "the system worked" in the case of Flight 253. Those ill-chosen words have caused much embarrassment for the White House, although officials say Ms Napolitano's job is safe.

But criticism is being directed at the Republicans, one of whose senators is singlehandedly holding up confirmation of Mr Obama's choice to head the Transportation Security Administration, the body responsible for air travel security in the US. Jim DeMint of South Carolina has for months been blocking the nomination of Erroll Southers – not because of any security concerns, but out of fear that Mr Southers might allow TSA workers to join a trade union.

In the meantime the Pentagon is weighing an increase in strikes against the Yemen operations of the al-Qa'ida affiliate there, which has claimed responsibility for the 25 December attack. Abdulmutallab had two spells in Yemen, in 2004 to 2005 and then between August and December this year, when he was trained for last week's attack.

Officials here reckon that between 200 and 300 al-Qa'ida operatives are based in Yemen, and Abdulmutallab reportedly has told interrogators that many others like him are being trained for attacks. But after a series of recent strikes both in collaboration with Yemeni security forces and by unarmed drones, US commanders are unsure how many militants may have been killed, or whether the local al-Qa'ida leadership has scattered, at least temporarily.

But given Mr Obama's vow earlier this week that the US would not rest "until we find all who were involved," some increase in US-led counter-terrorism operation in Yemen seems sure.

Yesterday meanwhile, Nigeria joined the Netherlands in announcing that it plans to equip its international airports with full-body scanners to counter the enhanced terrorist threat. The machines, which use radio waves to generate a picture of the body that can see through clothing and spot hidden weapons or packages, will be installed next year, the Nigerian aviation chief Harold Demuren said.

Earlier the Interior Minister of the Netherlands, Guusje Ter Horst, said that her country's international airports it will begin using the scanners for flights heading to the United States immediately. "It is not exaggerating to say the world has escaped a disaster," she told a news conference.

* It emerged last night that Abdulmutallab spent two weeks in Houston last year attending a seminar conducted by an internet-based Islamic education center. Waleed Basyouni, vice-president of the AlMaghrib Institute, said Abdulmutallab registered online in April 2008, then attended a two-week programme hosted by the institute in Houston four months later. Records show the Nigerian identified himself as a 21-year-old student at UCL and the London School of Economics.

Terror threat Somali suspect held

A man tried to board a commercial airliner in Mogadishu, Somalia, last month carrying powdered chemicals, liquid and a syringe that could have caused an explosion in a case bearing similarities to the terrorist plot to blow up a Detroit-bound airliner, officials said yesterday.

The Somali man, whose name has not yet been released, was arrested by African Union peacekeeping troops before the Daallo Airlines flight took off on 13 November. It had been scheduled to travel from Mogadishu to the northern Somali city of Hargeisa, then to Djibouti and Dubai. A Somali police spokesman, Abdulahi Hassan Barise, said the suspect was in Somali custody.

Catalogue of failures: How Abdulmutallab slipped through the net

* Umar Farouk Abdulmutallab's father went to the US embassy in Nigeria a month before the failed attack, to confide his worry over his son's "radical views".

* He reportedly had a face-to-face meeting with a CIA official which he followed up with several calls.

* A senior White House official said intelligence officials also picked up "chatter" among al-Qa'ida members referring to a possible attack by "a Nigerian".

* They had already received warnings about a possible Christmas Day attack.

* After his father's visit, Abdulmutallab's name was put on the CIA's list of 550,000 people with "possible links to terrorism", but intelligence was not shared, and his name was not put on the list of 18,000 from which the "no-fly" list of 4,000 is taken.

* His multiple-entry US visa was not revoked, and no alarm bells were sounded when he bought his one-way ticket with cash, in Accra, Ghana, and only carried hand baggage.