Ibrahim Hassan al-Asiri has built a reputation as al-Qaida's bomb-making savant one potential near miss at time: Explosive-rigged underwear aboard a Christmas flight to the U.S. in 2009, printers fitted with high-grade explosives the next year and now possibly a metal-free device that could avoid airport detectors.
Before those failed attempts, he staged an even more audacious attack: Turning his own brother into a suicide bomber in a mission that injured Saudi Arabia's top counterterrorism official and was later decried by the U.S. State Department for its "brutality, novelty and sophistication."
"You tyrants ... your bastions and fortifications will not prevent us from reaching you," said an al-Qaida statement claiming responsibility for the August 2009 blast in Jiddah.
This appears to be the essence of al-Asiri's plots as one of the leaders of the Yemen-based Al-Qaida in the Arabian Peninsula, or AQAP. A pattern has emerged of explosive expertise channeled into designs using a smuggler-style stealth and innovation to try to outwit security forces and spy agencies.
U.S. authorities Tuesday probed the latest device believed to be the work of the Saudi-born al-Asiri or one of his students after it was uncovered in a CIA operation. It was described as a refinement of the underwear bomb that failed to detonate aboard a jetliner over Detroit on Dec. 25, 2009. The twist this time was an absence of metal, which could have made the device undetectable by conventional airport scanners.
"It was a threat from a standpoint of the design," said John Brennan, President Barack Obama's counterterrorism adviser.
Al-Asiri, 30, arrived in Yemen in 2006 after being jailed by Saudi officials in crackdowns against Islamic militants.
"They put me in prison and I began to see the depths of (the Saudi) servitude to the Crusaders and their hatred for the true worshippers of God, from the way they interrogated me," he is quoted as saying in the September 2009 issue of Sada al-Malahem, or Voice of Battles, an Arabic-language online magazine put out by al-Qaida's branch in Yemen.
His younger brother, Abdullah, also made the trek to Yemen as they turned their backs on their father, a four-decade veteran of the Saudi military.
In Yemen's rugged northern mountains, they met with fugitive Yemeni militant Nasser al-Wahishi, a former aide to Osama bin Laden, and became the nucleus of the new al-Qaida affiliate, said the magazine account, which could not be independently confirmed.
They later brought in U.S.-born cleric Anwar al-Awlaki as a powerful propaganda voice in the West. Al-Awlaki was killed in a U.S. airstrike last September.
U.S. intelligence officials at first believed al-Asiri also was killed in the attack, but the suspicions were proven wrong several weeks later.
In August 2009, al-Asiri was linked to an elaborate scheme to strike at the heart of Saudi's intelligence services. His brother Abdullah posed as a disenchanted militant wishing to surrender to high-ranking officials in his homeland. A Saudi royal jet was dispatched. To avoid detection, the explosives where reported hidden in his rectum or held between his legs.
Once inside the Saudi intelligence offices in the Red Sea port of Jiddah, he detonated the device near his target: Deputy Interior Minister Prince Mohammed bin Nayef _ whose father Prince Nayef ran the ministry and would later become the kingdom's heir to the throne.
Prince Mohammed was slightly injured in the suicide blast. The bomb used an industrial explosive known as PETN, or pentaerythritol tetranitrate, the same material used in 2001 by convicted shoe bomber Richard Reid when he tried to destroy a trans-Atlantic flight.
It would become a signature element of al-Asiri's plots, according to intelligence analysts.
After the failed Christmas 2009 bombing, investigators pulled al-Asiri's fingerprint off the bomb hidden in the underwear of the Nigerian-born suspect, Umar Farouk Abdulmutallab, aboard the Northwest Airlines flight.
Less than a year later, al-Asiri was linked to the discovery of printer cartridges packed with PETN and sent by international courier with Chicago-area synagogues listed as the destination. The explosive-rigged packages _ believed powerful enough to bring down a plane _ were pulled off airplanes in England and the United Arab Emirates.
Al-Asiri became a major focus of America's anti-terrorism efforts. In March 2011, Washington officially designed al-Asiri as a wanted terrorist, calling him the primary bombmaker for AQAP. It also presumably puts al-Asiri among the chief targets on the U.S. hit list.
Last month, U.S. officials expressed concern that al-Qaida "intends to advance plots along multiple fronts, including renewed efforts to target Western aviation," according to a joint intelligence bulletin circulated from the U.S. Northern Command, the FBI and Homeland Security Department.
While al-Asiri has been dubbed the master bomb-maker of al-Qaida's Yemen franchise, it may be wrong to label him the linchpin of the group's ability to strike with explosives, said Gregory Johnsen, a Yemen expert at Princeton University.
"I think it is safe to assume that in the nearly six years that he has been in Yemen, he has trained other individuals to replace him if he were to be killed," Johnsen wrote on his blog Tuesday. "It is unlikely that Asiri is the only bombmaker AQAP has within its ranks _ he is just the only name we know."