"We had the skill set, the systems and the techniques, and we needed to move backwards in time," McAleenan said.
Since the Sept. 11 attacks, the terror watch list and its derivative, the no-fly list, became some of the government's best-known counterterrorism tools. They also became some of the most criticized, as innocent travelers were inconvenienced when they were mistaken for terrorism suspects. Outrage forced the government to pare the lists, which airlines checked before allowing people to fly.
After the attempted Christmas attack, the intelligence community took a closer look at the names on the terror watch list and set new standards for adding names. The watch list and no-fly list are constantly reviewed, and names are added and removed each day. There are about 30,000 people on the no-fly list and a companion list for people who must receive extra screening at airports, a counterterrorism official told the AP.
The more expansive terror watch list includes about 450,000 names of people the U.S. intelligence community believes are, or could be, a threat to national security because of terrorist ties. Some of the people on the watch list are still being investigated, and there is not enough information for the government to arrest them.
The new policy has not turned the 450,000-person terror watch list into the no-fly list. Simply being on the terror watch list does not mean a person won't be allowed to enter the U.S., McAleenan said. When CBP reviews passenger lists and matches someone on the terror watch list, CBP will review information available on the person before it recommends to the airline whether the person can board the plane, McAleenan said. In most cases, if CBP recommends against allowing the passenger to board, it's because the person would be turned away upon arrival inside the United States due to security concerns.