WASHINGTON - As the Pentagon warns of the security risks posed by social networking sites, newly released government documents show the military also uses these Internet tools to monitor and react to coverage of high-profile events.

The U.S. Air Force tracked the instant messaging service Twitter, video carrier YouTube and various blogs to assess the public backlash to the Air Force One flyover of the Statue of Liberty this spring, according to the documents.

While the attempts at damage control failed -- "No positive spin is possible," one PowerPoint chart reads -- the episode opens a window into the tactics for operating in a boundless digital news cycle.

This new terrain has slippery slopes for the American military. Facebook, MySpace and other social media sites are popular among service members, including those in Iraq and Afghanistan who want to keep in touch with friends and family. The sites are also valued by military organizations for recruiting or communicating with other federal agencies.

But posting information on them makes it vulnerable to being lost or stolen, according to Pentagon officials. On Thursday hackers shut down Twitter for several hours, while Facebook had intermittent access problems -- an indication of the shortcomings of relying on these services.

The Marine Corps' computer network blocks users from accessing social media sites, which service officials say expose "information to adversaries" and provide "an easy conduit for information leakage."

That prohibition might extend to other parts of the U.S. military pending a top-level review ordered in late July by Deputy Defence Secretary Bill Lynn. In a memo, Lynn said such sites are important tools but more study is needed to understand their threats and benefits.

Air Force officials are already aware of the potential benefits.

According to the Air Force One documents released through the Freedom of Information Act, a unit called the Combat Information Cell at Tyndall Air Force Base in the U.S. state of Florida monitored the public fallout from the April 27 flight over the Statue of Liberty and offered recommendations for dealing with the fast-breaking story.

The presidential plane took off for New York from Andrews Air Force in the state of Maryland accompanied by two F-16 jet fighters. The purpose of the flight, which wasn't publicly announced, was to get new photos of the specially modified Boeing 747 with the statue in the background.

The mission became a public relations disaster as panicked New Yorkers, fearing another 9/11-style attack, emptied office buildings. In the aftermath, Louis Caldera, director of the White House military office that authorized the flight, was fired.

The Combat Information Cell's first assessment of the event said "Web site blog comments 'furious' at best." Local reporting of the flyover was "very critical, highlighting scare factor," it added.

A Twitter search revealed a rate of one "tweet" per minute about a pair of F-16s chasing a commercial airliner. A tweet is a text message of up to 140 characters delivered to the author's subscribers, who are known as followers.

Media coverage over the next 24 hours "will focus on local hysteria and lack of public notification," the cell predicted. "Blogs will continue to be overwhelmingly negative."

"Damage control requires timely counter-information," but the opportunity for that had passed, the assessment said. The cell recommended acknowledging the mistake and ensuring it didn't happen again.

An update on April 28 said the story was still "reverberating, surprisingly resilient." The tweet rate had grown to three per minute and the words "New York" had been pushed into Twitter's high-frequency topic category. Videos of the event posted on YouTube had been viewed more than 260,000 times, it said.

1st Air Force spokesman Al Eakle explained that the command had no role in planning or co-ordinating the Air Force One flight. But the units tracked social networks and blog traffic "to obtain what lessons we might learn so as not to repeat them in the future." The assessments were sent to the command's leadership so they'd know how the public was reacting, he added.

John Verdi of the Electronic Privacy Information Center in Washington said grey zones can emerge while monitoring social networking sites because participating is based on trust.

"Lots of times individuals upload private or sensitive information that they expect to share with their friends or family and not the whole Internet world," Verdi said. "It would certainly be a major problem if the government were accessing that information under false pretenses."

Paul Bove, an Air Force digital media strategist, said service personnel are instructed not to do that. Nor are they to use aliases or represent a position that's beyond the scope of what they do.

"We always tell people, 'Stay in your lane and don't talk about something that you're not qualified to talk about,"' Bove said.