A top secret, offensive military operation, led by the U.S. Special Operations Command, beginning around 1998, targeted against al Qaeda.
The first stage of Abel Danger was a data mining operation to determine the structure of the Al Qaeda network. This finished by February 2001.
The 911 Commission chose to ignore Able Danger.
In their book "Without Precedent", 9/11 Commission leaders Thomas Kean and Lee Hamilton said the information had been investigated but didn't stand up:
Another item that surfaced in early July was the "Able Danger" Department of Defense surveillance program that our staff had been briefed on in Afghanistan. On July 12, Dietrich Snell interviewed Captain Scott Phillpott, who requested the meeting. At that point, our staff had received all of the Department of Defense documents on Able Danger and had found no mention of Atta, though there had been mention of the al Qaeda operative Mohammed Atef.
Phillpott told Snell he recalled seeing the name and photo of Mohammed Atta on an "analysts notebook chart" involved in Able Danger before 9/11 - in other words, Able Danger had managed to get Mohammed Atta under surveillance. Phillpott said he saw this chart only briefly, and that it dated from the period February - April 2000.
There was no documentary evidence whatsoever to back up Phillpott's sensational claim. Phillpott himself had not performed the analysis, not could he explain what information had led to this supposed identification of Atta by Able Danger. In addition to the lack of documentary evidence from Able Danger, there was no corroboration of Phillpott's account by any information from within the U.S. government, or by German government sources that had tracked the Hamburg cell. Phillpott's account also failed to match up with detailed evidence compiled by our staff documenting Atta's travels, activities, and entry into the United States, including from the INS and State Department records. Snell concluded that the officer's account was not sufficiently reliable to warrant inclusion in the report or further investigation. This conclusion was not a challenge to Captain Phillpott's good intentions; the tip he provided just did not check out.
Page 294-295 Without Precedent Thomas Kean and Lee Hamilton
The CIA also had a war plan. It is not clear if this was the same thing as Able Danger:
In December 1998 CIA chief Tenet "declared war" on Osama bin Laden. Early in 1999 Tenet "ordered the CTC to begin a 'baseline' review of the CIA's operational strategy against bin Laden". In the spring he "demanded 'a new, comprehensive plan of attack' against bin Laden and his allies".
The CTC had produced a "comprehensive plan of attack" against bin Laden and previewed the new strategy to senior CIA management by the end of July 1999. By mid-September, it had been briefed to CIA operational level personnel, and to the NSA, the FBI, and other partners. The strategy was called simply, 'the Plan'.
Cofer Black and his new bin Laden unit wanted to "project" into Afghanistan, to "penetrate" bin Laden's sanctuaries. They described their plan as military officers might. They sought to surround Afghanistan with secure covert bases for CIA operations — as many bases as they could arrange. Then they would mount operations from each of the platforms, trying to move inside Afghanistan and as close to bin Laden as they could to recruit agents and to attempt capture operations. Black wanted recruitments and he wanted to develop commando or paramilitary strike teams made up of officers and men who could "blend" into the region's Muslim populations.
Parallel with these developments, in November–December 1999 Mohamed Atta, Marwan al-Shehhi, Ziad Jarrah, and Nawaf al-Hazmi visited Afghanistan, where they were selected for the "planes operation" that was to become known as 9/11. Working with a Malaysian security unit, the CIA watched al-Hazmi and his companion Khalid al-Mihdhar as they attended a Qaeda conference in Kuala Lumpur in January 2000, later determined to be where decisions about the "planes operation" were made.