F.A.A. Alerted on Qaeda in '98, 9/11 Panel Said

American aviation officials were warned as early as 1998 that Al Qaeda could "seek to hijack a commercial jet and slam it into a U.S. landmark," according to previously secret portions of a report prepared last year by the Sept. 11 commission. The officials also realized months before the Sept. 11 attacks that two of the three airports used in the hijackings had suffered repeated security lapses.

Federal Aviation Administration officials were also warned in 2001 in a report prepared for the agency that airport screeners' ability to detect possible weapons had "declined significantly" in recent years, but little was done to remedy the problem, the Sept. 11 commission found.

The White House and many members of the commission, which has completed its official work, have been battling for more than a year over the release of the commission's report on aviation failures, which was completed in August 2004.

A heavily redacted version was released by the Bush administration in January, but commission members complained that the deleted material contained information critical to the public's understanding of what went wrong on Sept. 11. In response, the administration prepared a new public version of the report, which was posted Tuesday on the National Archives Web site.

While the new version still blacks out numerous references to particular shortcomings in aviation security, it restores dozens of other portions of the report that the administration had considered too sensitive for public release.

The newly disclosed material follows the basic outline of what was already known about aviation failings, namely that the F.A.A. had ample reason to suspect that Al Qaeda might try to hijack a plane yet did little to deter it. But it also adds significant details about the nature and specificity of aviation warnings over the years, security lapses by the government and the airlines, and turf battles between federal agencies.

Some of the details were in confidential bulletins circulated by the agency to airports and airlines, and some were in its internal reports.

"While we still believe that the entire document could be made available to the public without damaging national security, we welcome this step forward," the former leaders of the commission, Thomas H. Kean and Lee H. Hamilton, said in a joint statement. "The additional detail provided in this version of the monograph will make a further contribution to the public record of the facts and circumstances of the 9/11 attacks established by the final report of the 9/11 commission."

Bush administration officials said they had worked at the commission's request to restore much of the material that had been blacked out in the original report. "Out of an abundance of caution, there are a variety of reasons why the U.S. government would not want to disclose certain security measures and not make them available in the public domain for terrorists to exploit," said Russ Knocke, spokesman for the Department of Homeland Security.