The Islamic State group and its bomb makers are intent on blowing up passenger jets, the House Homeland Security Committee chairman said Monday.

Rep. Michael McCaul, R-Texas, said the terror group’s efforts to target airlines are among the “most disturbing” and pressing national security threats facing the country, and immediate action is required to shore up security at airports.

The group’s virtual military defeat in Iraq and Syria has led its fighters and bomb makers to flee across the globe where they continue to plot such attacks, said McCaul, who delivered the warning as part of a national security address at George Washington University.

“The crown jewel is aviation and they are still seeking to blow up airplanes even though they might not be able to hijack it,” he said.

The Department of Homeland Security temporarily banned laptops on flights from some countries last year amid revelations that terrorists were seeking to turn personal electronic devices into bombs.

“I can’t go into the classified space of where they are but we know they are out there. We know they’re intent on making these bombs. The threat was actually worse than I thought,” said McCaul, whose committee received briefings. “I found this to actually be one of the most disturbing, and quite frankly what keeps you up at night, question.”

The threat is also complicated by the lack of security at key foreign airports including those in Istanbul and Cairo that see high volumes of passengers traveling to the United States, McCaul said.

“I can tell you, these are not secure airports,” he said.

The U.S. must deploy more next-generation airport security scanners that use a 3-D technology called computed tomography, McCaul said. The MRI-like devices provide more detailed imagery and can even highlight explosive materials, compared to the two-dimensional black-and-white imagery produced by X-ray scanners.

“I've seen these devices. They work,” McCaul said.

The White House Office of Budget and Management has halved a Transportation Security Administration request to purchase 300 of the machines for $150 million. McCaul said expanding the use of the technology has also been caught up in bureaucratic red tape.

“I know everyone on the committee on both sides of the aisle see this as, like, a ‘not on our watch’ type thing. This is not going to happen on our watch and we are going to fully deploy it,” he said. “I see this as one of the biggest threats and something we need immediate action on. Congress is doing that and I know the TSA administrator wants that, we just have to back him.”