A "next generation" device that could have slipped past airport security, and the evil genius behind it

Jonathan Ernst / REUTERS Transportation Security Administration chief John Pistole

For many Americans, airline security is an onerous and even excessive burden. But in remarks at a national security forum on Friday, Transportation Security Administration chief John Pistole illustrated why the federal government is still on high alert. Speaking in unusual detail, Pistole offered specifics about an underwear bomb devised by a master al Qaeda bomb-maker in Yemen meant to be exploded in an airliner over the United States last year. The plot was foiled thanks to a double-agent inside al Qaeda’s Yemen branch, in a case that has also become the subject of a controversial Justice Department leak investigation.

In an exchange with ABC News reporter Brian Ross at the 2013 Aspen Security Forum, Pistole described the bomb as “Underwear 2,” a successor to the underwear bomb worn Umar Farouk Abdulmutallab tried to detonate on Northwest Flight 253 near Detroit on Christmas Day 2009. Abdulmutallab’s bomb fizzled, severely injuring his groin but no one else.

Pistole described the May 2012 bomb as “a next generation device” that was “new and improved in many respects” from the Christmas 2009 bomb. Designed by one of the most wanted terrorists in the world, Ibrahim al-Asiri, the device featured “a new type of explosive that we had never seen,” Pistole said. “All of our explosive detection equipment… wasn’t calibrated to detect that. And all of our 800 bomb-sniffing dogs had not been trained for that specific type.”

The use of a new explosive has been previously reported, but Pistole continued with less familiar details about Underwear 2 that reflect the growing sophistication of Asiri’s sinister craftsmanship. He said the device included redundancy, by mean of two different syringes to mix liquid explosive compounds–“a double initiation system,” apparently a response to a failure of Abdulmutallab’s initiation process. In essence, Pistole said, “they made two devices.”

Finally, Pistole said, the new bomb was encased in simple household caulk in an effort to trap vapors that might alert any bomb-sniffing machines or dogs that did happen to be capable of identifying the explosive.

“So you really have a twisted genius in Yemen,” Ross observed. “That is our greatest threat,” Pistole replied. “All the intel folks here [at the forum] know that is a clear and present danger.”

Pistole added that Asiri is thought to have trained other bomb-makers in his dark arts, and that count-terror officials are intensely focused on tracking down the mentor and his students.

In an interview after his remarks, Pistole said TSA has adjusted its bomb-sniffing defenses in response to Underwear 2: “They’ve been recalibrated.” But his concern about Asiri and his cohorts in Yemen endures. “They want to show that we can spend billions and billions of dollars,” Pistole told Ross, “and we still can’t stop them.”