A draft investigative report by the House Judiciary Committee, obtained by ABC News, finds that terrorists could easily spot undercover federal air marshals because of airport boarding policies Homeland Security has "been oblivious to" or refused to change.
"Any procedure that could potentially compromise the anonymity of a federal air marshal is a risk to national security," concludes the report to be made public next week.
Current and former air marshals tell ABC News their own bosses are responsible for blowing their cover.
"I would say that any well trained terrorist organization could identify every air marshal at ever airport in the country," former air marshal supervisor Don Strange told ABC News for a program to be broadcast tonight on 20/20.
A three-month undercover investigation found five separate places at airports where air marshals are required to identify themselves in front of waiting passengers.
The investigation also found air marshals are required to stay in the same hotels, which often advertise their presence.
"Welcome Federal Air Marshals, Company of the Month" read the sign outside a Sheraton hotel in Florida.
At a Holiday Inn, a list of the air marshals with their names and room numbers was kept in public view at the front desk.
"Anybody who wants to do something bad to a plane and its passengers knows who they have to subdue first," Congressman Jim Sensenbrenner, the Chairman of the House Judiciary Committee, told ABC News.
Sensenbrenner urged ABC News to broadcast its undercover footage of security gaps in order to change policies that compromise the air marshals.
"This has got to stop," he said.
The Federal Air Marshal Service declined to "be interviewed or participate in any way with ABC News."