© NBC NewsAlleged - Firebrand, Explosive Devices, Master Mind, Bomb-Maker, Terrorist, Ibrahim al-Asiri.
The CIA foiled a plot by al-Qaida's affiliate in Yemen to bomb a U.S.-bound airliner this month, senior U.S. officials told NBC News.

Comment: What Official? Does an official - official have an official name?

Officials said the plot involved a bomb that improved on the one that had been sewn into the underpants of Umar Farouk Abdulmutallab, who failed in a plot to blow up a Detroit-bound airliner on Christmas Day 2009. That device did not detonate.

Comment: A new and improved Underwear bomb. Have they switched from boxers to briefs?

This bomb had a more refined detonation mechanism and was "totally non-metallic," which officials told NBC News would have made it more difficult to detect by traditional screening processes.

Comment: Thus, we are indirectly being told that (soon) everyone will be needing to use the Body Scanner.

A U.S. counterterrorism official told NBC News there were "refinements on reliability" in particular that made this bomb more sophisticated and more likely to explode.

Comment: How much sophistication can a man stuff into a pair of underwear? Are our minds too feeble to be allowed a generalized schematic?

In addition to being a threat to commercial planes, the official said this type of bomb could be used in crowded places, on other transportation systems or for assassinations.

The official noted that the bomb "was never near a plane" and "never posed a risk." The plot was disrupted well before it threatened Americans or U.S. allies, the official added.

The U.S. received the device last month. The FBI is currently conducting technical and forensics analyses on it.

The official would not specify which international security service provided the intelligence that led to the unraveling of the plot, as there is concern about retaliatory attacks against U.S. targets inside Yemen.

Counterterror officials deem the thwarted plot a "success story," NBC News reported. The FBI said in a statement that the successful operation was the "result of close cooperation with our security and intelligence partners overseas."

According to The Associated Press, 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. official, who spoke on condition of anonymity because of the sensitive nature of the case, said the individual is not a threat but would not say where he is located. He did not provide information about the individual's nationality or age.

It's unclear who built the bomb, but the device does bear similarities to other explosive devices built by master bomb-maker Ibrahim al-Asiri. However, Asiri may not have been directly involved in this plot.

According to one official, there is "evidence that Asiri has passed along his bomb-making knowledge to others." The official would not say whether Asiri or an apprentice were involved in this plot.

In an exclusive meeting, a senior U.S. intelligence official told NBC News that Asiri 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.

Asiri is not just a bomb maker but has also taken to "training the trainers," sharing his skills with others. Officials believe he is responsible for this bomb, the one sewn into Abdulmutallab's underwear and the one used during the attempted assassination attempt of Nayef. As director of Saudi counterterrorism, Nayef is one of the United States' most trusted allies in the fight against al-Qaida.

For each bomb, officials are seeing a new level of refinement and sophistication.

The U.S. counterterrorism official said the thwarted attack and the recent drone death of Fahd al-Quso, an FBI "most-wanted terrorist," was a "one-two body blow" to al-Qaida in the Arabian Peninsula, which U.S. officials have recently described as the most aggressive of the al-Qaida franchises.

They also believe that al-Quso, director of external communications for the franchise, would have had to approve the planned May attack.

Officials also say the plot had no apparent ties to the anniversary of the killing of bin Laden. One official told NBC News the timing was coincidental.

A White House statement said President Obama was told of the plot in April.

"The disruption of this IED (improvised explosive device) plot underscores the necessity of remaining vigilant against terrorism here and abroad," the statement read.

The Associated Press contributed to this report.