Amid concerns of an Al-Qaeda effort to create an undetectable bomb, the US has ordered tighter security at some airports in Europe and the Middle East offering direct flights to the United States.
On Wednesday, Secretary of Homeland Security Jeh Johnson said he directed the Transportation Security Administration to put more security measures in place after sharing “recent and relevant” information with foreign allies.
"Aviation security includes a number of measures, both seen and unseen, informed by an evolving environment," Johnson said in a statement. "We will continue to adjust security measures to promote aviation security without unnecessary disruptions to the traveling public.”
American intelligence has picked up indications that bomb makers from Al-Qaeda's Yemen affiliate, Al-Qaeda in the Arabian Peninsula (AQAP), have traveled to Syria to link up with the Al-Qaeda affiliate there, al-Nusra Front. The groups are working to perfect an explosive device that could foil airport security, a counterterrorism official told the Associated Press.
The move was not unexpected, as intelligence agencies, including the Department of Homeland Security and the FBI, have been debating their options for months, and top-level officials met at the White House last week to discuss the issue.
“[This threat] is different and more disturbing than past aviation plots," one source told ABC News earlier this week.
Radical Muslims traveling to war-torn Syria and Iraq pose a threat to Western nations because they will be able to enter the countries without visas on European passports.
"We've seen Europeans who are sympathetic to their cause traveling into Syria and now may travel into Iraq, getting battle-hardened. Then they come back," President Barack Obama told NBC News in an interview broadcast Sunday.
Officials are concerned that bombs made with non-metallic explosives could be surgically implanted in jihadists’ bodies. Previous attempts by AQAP have involved suicide bombers with explosives hidden in their underwear on commercial flights and hidden in printer cartridges on cargo flights.
One of the places with heightened security will be British airports. “The beefed up security will fuel fears of massive queues at airports over the summer although the Department for Transport said the extra measures - which have not been disclosed - were not expected to cause ‘significant disruption’ and noted that the official UK threat status remained unchanged,” the Telegraph reported.
The measures may include closer scrutiny of personal electronics and footwear, but government officials would not reveal any specifics.
"We have taken the decision to step up some of our aviation security measures. For obvious reasons we will not be commenting in detail on those changes,” a Department for Transport spokesman said. "The majority of passengers should not experience significant disruption. There will be no change to the threat level, which remains at substantial.”
"The safety and security of the public is our paramount concern. The UK has some of the most robust aviation security measures and we will continue to take all the steps necessary to ensure that public safety is maintained."
Asked Monday by ABC News whether his European counterparts were doing enough to address the threat emanating from Syria, FBI Director James Comey said European authorities are "doing a tremendous amount of work" but that it was "hard for [him] to say" whether it's enough to prevent the threat from materializing.