(CBS News) At more than 180 U.S. airports, the Transportation Security Administration increasingly relies on full-body scanners. Their electromagnetic waves screen passengers for dense objects -- both metallic and non-metallic threats -- from guns to homemade plastic explosives.
Kip Hawley was the TSA administrator in 2007, when the agency rolled out these scanners.
He believes an alert transportation security officer at an airport security checkpoint would have caught the latest underwear bomb, which washad been thwarted by the CIA before it came near an airport.
"The [officer] monitoring the image in a body scanner would be able to find enough to say there's something there we need to check," Hawley said.
The TSA has 700 full-body scanners in place across American airports.
But the vast majority of travelers -- more than nine in 10 -- pass through traditional magnetometers. Their metal-detection technology is less sophisticated than full-body scanners and would not detect PETN, the type of explosive used in this latest threat.
PETN was also used in the failed 2009 Christmas Day underwear bomb plot. Umar Farouk Abudulmutallab went from Lagos, Nigeria to Amsterdam, and never passed through a full-body scanner on his way to Detroit.
In 2010, TSA Administrator John Pistole took CBS News to an agency lab, to demonstrate the threat posed by PETN.
He described the explosive as "very concealable, moldable, designed in such a way that unless you have an advanced imaging technology, you walk through a metal detector and it's not going to register."
Hawley also wants the TSA to change its security approach, and focus on the primary threat: explosives.
"Clearly a [transportation security officer] who has less to do in terms of fishing through bags for Swiss army knives -- and is able to focus on the explosive threat, on behavior related to that, on resolving suspicious circumstances. I think that is a key ingredient to security and needs to continue," Hawley said.
Security experts agree the best way to stop any bomber is to have good intelligence - spotting the threats before they ever get to an airport.
That's exactly what happened in the most recent underwear bomb plot.