A six-year-old article mistakenly seen by Bloomberg financial news users Monday reported the bankruptcy of United Airlines and triggered a massive sell-off that nearly obliterated the company's stock in a matter of minutes.

The light-speed wipeout is a powerful reminder of how quickly bad information can spread via the Internet to a trigger-happy Wall Street that is willing to dump millions in stock before checking the facts.

It exposed the vulnerability of Bloomberg's influential brand name to bogus content -- the old article was posted to a Bloomberg subscription service by a Florida investment adviser, one of Bloomberg's many "third-party content-providers." Moments later, it popped up under United Airlines company news as a headline only: "United Airlines files for Ch. 11 to cut costs."

And it showed how the imperfect technologies of Internet searches combined with human failure can cause ruinous results.

United parent company UAL opened trading on the Nasdaq Stock Market Monday at $12.17 per share. The 2002 bankruptcy article appeared on Bloomberg monitors on Wall Street just before 11 a.m.

In the minutes that followed, some 15 million shares of UAL traded and the stock plunged to $3 per share. Trading was halted at 11:30 a.m. for an hour.

The stock closed down $1.38 at $10.92 Monday.

United said it is unsure whether the incident will cause the already-shaky airline material damage.

At United's Chicago headquarters Monday morning, the airline's financial services division watched in horror as the stock plummeted, while its shocked media relations department was besieged by reporters asking why the company had declared a surprise bankruptcy, only six years after its last one.

UAL filed for bankruptcy protection in 2002 and emerged in 2006.

The bizarre chain of events began early Monday, when a reporter at Income Securities Advisors -- a Miami- based investment service that disseminates news about distressed companies -- typed in a Google search: "bankruptcy 2008."

Up popped the six-year-old article from the South Florida Sun-Sentinel, which originally appeared in the Chicago Tribune on Dec. 10, 2002, the day after United declared bankruptcy. Tribune Co. owns the Tribune and the Sun-Sentinel.

The cascade of failure may have stopped there had the article carried its correct publication date. Instead, it was undated.

Late Monday night, Tribune Co. provided a screen shot showing the six-year-old story appearing on Google News with a Saturday, Sept. 6, 2008, date. Tribune spokesman Gary Weitman said he thinks Google somehow pulled the old, undated story from the Sun-Sentinel online archive and assigned it a date of Sept. 6, 2008 -- the date Google found it.

Google provided screen shots of its own Monday night showing the undated old article on the Sun-Sentinel's site on Sunday, Sept. 7, under the heading "most viewed business stories," which may have resulted from the increased traffic caused by the article's inclusion in Google News, Weitman said.

This, in turn, may have caused it to pop up when the reporter from Income Securities Advisors typed in "bankruptcy 2008."

In the mind of the reporter, Wall Street would want to know about a major airline declaring bankruptcy. The reporter posted the story to the Bloomberg Professional service at 10:53 a.m. Monday.

Six minutes later, Bloomberg posted a news article headlined: "UAL Shares drop 33% at 10:58 a.m."

At 11:16 a.m., Bloomberg posted a correction in several languages, highlighted in red on the company's proprietary monitors: "UAL SAYS IT HASN'T FILED FOR CHAPTER 11."

"It shows the market apparently reacts to a headline as much as anything else," said Richard Lehmann, president of Income Securities Advisors.

Lehmann said Monday's mistake was the first at his firm in 10 years. He was reluctant to heavily criticize his reporter, but said, "It would have been nice if the reporter had been more grounded in what's going on out there in the world."

"The fact that this happened with a major corporation like United based on one headline coming across Bloomberg, that you'd get this kind of knee-jerk reaction, there's something wrong with the trading mechanism," Lehmann said.

Income Securities Advisors is one of many "third-party" contributors to Bloomberg Professional, a subscription service used by Wall Street traders.

The Bloomberg Professional service is an Intranet limited to subscribers, who see news stories and financial information provided by Bloomberg employees, as well as content from third-party contributors, such as the six-year-old story mistakenly posted by Income Securities Advisors.

"The closest analogy would be a television network's content being carried by a cable carrier," Bloomberg spokeswoman Judith Czelusniak wrote in an e-mail Monday.

Bloomberg had no further comment on Monday's incident, she said.

Lehmann said he started getting phone calls shortly after his company posted the story from the Sun-Sentinel. Once he realized what had happened, he moved quickly -- he called Bloomberg and had the six-year-old story removed at 11:08 a.m. About 20 minutes later, Nasdaq halted trading.

In a statement, Nasdaq said all trades during the chaotic period from 10:55 -- two minutes after the story was posted -- to 11:08 would stand and had no further comment.

United said it has demanded a retraction from the Sun-Sentinel and is launching an investigation.