The 8-year-old system, with its rainbow of five colors -- from green, signifying a low threat, to red, meaning severe -- became a fixture in airports, government buildings and on newscasts. Over the past four years, millions of travelers have begun and ended their trips to the sound of airport recordings warning that the threat level is orange.
The system's demise would not be the end of terror alerts; instead, the alerts would become more descriptive and not as colorful. In the past two years, Obama administration officials have changed security protocols without changing the color of the threat, such as introducing new airport security measures after a terrorist tried to bring down a Detroit-bound jetliner last Christmas.
By scrapping the colors, President Barack Obama would abandon a system that critics long have said was too vague to be useful and that Democrats criticized as a political scare tactic. And it would represent a formal undoing of one of the George W. Bush administration's most visible legacies.
Transportation Security Administration chief John Pistole said on ABC's "Good Morning America" that he believes the aim of the administration's plan is to help people better understand concepts about danger that may be too vague when conveyed through the color-coded system.
"I think it's something that is under review to make it meaningful and relevant to the American people," he said. "I'm just not sure how relevant it is."
He called Homeland Security Secretary Janet Napolitano's internal review "just a commonsense approach" and said she should be credited with "making some judgments going forward."
Officials confirmed the recommendation and the draft proposal was described to The Associated Press on condition of anonymity because other federal agencies are privately weighing in on the idea, and no final decision has been made.
Napolitano ordered a review of the system in July 2009. Earlier this year, the department decided the best way forward would be to scrap the colors and use more descriptive language to talk about terror threats. The recommendation is not related to the recent furor over airport security pat-downs and body scans.
The details of the new alert system -- including the words that would be used to describe the threats -- are still being worked out internally by multiple government agencies and the White House.
The Homeland Security Department would not discuss the recommendations and did not know when a new system would be rolled out. The current colored system remains in place.
"We are committed to providing specific, actionable information based on the latest intelligence," department spokeswoman Amy Kudwa said.
One of the recommended names for the new system is the National Terrorist Advisory System, replacing the current Homeland Security Advisory System.
An option under consideration is to go from five threat tiers to two: elevated and imminent. Under that model, when the threat level changes to imminent, government officials would be expected to be as specific as possible in describing the threat without jeopardizing national security. And an imminent threat would not last longer than a week, meaning the public wouldn't see a consistently high and ambiguous threat level.
There also would be an understanding with the public that there is a baseline level of vigilance needed in the U.S., but when the government gets information that suggests the threat is more specific, the new system would be used to communicate those details.
Former Homeland Security Secretary Tom Ridge has said the use of colors emerged from a desire to clarify the nonspecific threat information that intelligence officials were receiving after the 2001 terrorist attacks. The goal was to put the threat in terms the public could understand.
"And most importantly, it empowers government and citizens to take actions to address the threat," Ridge said in March 2002 when, as Bush's homeland security adviser, he announced the birth of the system.
Each color signaled specific security measures to be taken at airports and other public places. From the beginning, Ridge said, officials knew the system would become the target of critics.
Late-night TV host Conan O'Brien chimed in just days after the announcement.
"Earlier this week, Homeland Security Adviser Tom Ridge announced a new color-coded warning system. A color-coded system to keep the public informed about disasters. Seems like a good idea," O'Brien said. "Yeah, apparently red is the highest alert, and it means Dick Cheney is about to eat a mozzarella stick."
As part of her review in 2009, Napolitano solicited comments from the public about the current system. Some of those commentators likened the color-coded system to the boy who cried wolf. Others criticized it for not following the natural color spectrum. Others wanted the system to be based on numbers as opposed to colors and to mirror the weather alerts familiar to communities across the country.
Under the current system, green, at the bottom, signals a low danger of attack; blue signals a general risk; yellow, a significant risk; orange, a high risk; and red, at the top, warns of a severe threat. The nation has never been below the third threat level, yellow -- an elevated or significant risk of terrorist attack.
While the colored descriptors haven't changed in eight years, the government has modified how it uses them. The government departed from blanket warnings in 2004 when it raised the threat level for the financial sector in New York, New Jersey and Washington, D.C. Previously, warnings would have applied across the country.
The terror threat to the U.S. continues to change, but the color of the threat is the same as it was in 2006: yellow for the country as a whole and orange for the aviation sector.