By NBC News and msnbc.com staff
The CIA foiled a plot by al-Qaida's affiliate in Yemen to bomb a U.S.-bound airliner around the one-year anniversary of the killing of its former leader Osama bin Laden, The Associated Press reported.
According to the report, American officials say the plot involved a bomb with an improved design that upgraded the underwear bomb taken aboard a jetliner over Detroit on Christmas 2009. That explosive device failed to detonate.
The AP reports the improved bomb had a more refined detonation mechanism, but was still intended to be hidden in a passenger's underwear.
An official told NBC News no airlines were ever at risk. The plot was disrupted well before it threatened Americans or U.S. allies, the official added.
Counter-terror officials deem the thwarted plot a "success story," NBC News reported. They said they are analyzing the device.
According to the AP, the would-be suicide bomber was instructed to buy a ticket on the airliner of his choosing and decide the timing of the attack.
The U.S. officials interviewed spoke on the condition of anonymity to discuss the sensitive case, according to the AP.
In an exclusive meeting, a senior U.S. intelligence official told NBC News that Hassan al-Asiri -- the so-called “master bomb-maker” for al-Qaida in Yemen -- posed the single most dangerous threat to the United States.
According to the official, Asiri is the most capable of carrying out al-Qaida’s threat to launch a significant terrorist attack to kill Americans inside the United States.
Asiri designed the first underwear bomb that failed over Detroit and he was also the maker of the printer ink cartridge bombs that were discovered before they were shipped to the United States.
The senior official said counter-terrorism officials were seriously troubled by the ink cartridge bombs because they were “particularly sophisticated. “
Asiri has also implanted a bomb inside his brother in a failed attempt to assassinate Prince Mohammed bin Nayef, the Saudi deputy interior minister. The minister survived, but Asiri’s brother did not.
NBC News' Jim Miklaszewski and The Associated Press contributed to this report.
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