That test saw Department of Homeland Security Office of Inspector General operatives easily smuggle through fake weapons and explosives alike.
TSA pre-check travelers are exempt from the new screenings and can leave devices in their bags when traveling through the designated pre-check line, according to the TSA. Although this equipment has been tested at two airports, software installations has slowed progress toward expanding this at all US airports.
While the TSA catches scores of people with weapons - notably former Trump White House adviser Sebastian Gorka a year ago at Reagan National Airport - the inspector general's report in 2015 said that operatives from the office penetrated airport security in about 95 percent of their attempts.
The latest tests come just two years after the DHS secretly audited the agency and found that it failed 95 percent of the time.
The Department of Homeland Security has since offered eight recommendations to improve checkpoint security.
When pressed to get the failure rate, ABC News was told by a source that 80 percent failure was "in the ballpark".More news: Ezekiel Elliott's 6-game suspension back on
More news: Syria not invited to Paris climate talks despite joining
More news: Apple may be working on an AR headset for 2020
The undercover findings and recommendations were made during a Wednesday, Nov. 8 House Homeland Security Committee.
"We take the OIG's findings very seriously and are implementing measures that will improve screening effectiveness at checkpoints", Pekoske said.
The TSA was tested recently to see if its screeners, equipment and security procedures were up to par - and the agency failed miserably, with an estimated success rate of about 20 percent, a report says.
"We found that briefing disturbing", House Homeland Security Committee Chair Michael McCaul (R-TX) said following the hearing, the Atlanta Journal-Constitution reports. "We are focused on staying ahead of a dynamic threat to aviation with continued investment in the workforce, enhanced procedures and new technologies".
New equipment available would create 3D images of luggage to help screeners spot unsafe items, but it's only in use at two airports so far.
Congress and the TSA both supported installing CT scanners in place of outdated checkpoint scanners, but current funding doesn't allow that step to be taken, TSA administrator David Pekoske told Congress, CBS reported.