The story...

On July 26, 2001, cbsnews.com reported that John Ashcroft had stopped flying on commercial airlines.

Ashcroft used to fly commercial, just as Janet Reno did. So why, two months before Sept. 11, did he start taking chartered government planes?

CBS News correspondent Jim Stewart asked the Justice Department.

Because of a "threat assessment" by the FBI, he was told. But "neither the FBI nor the Justice Department ... would identify what the threat was, when it was detected or who made it," CBS News reported.

The FBI did advise Ashcroft to stay off commercial aircraft. The rest of us just had to take our chances.
http://www.sfgate.com/cgi-bin/article.cgi?file=/gate/archive/2002/06/03/hsorensen.DTL

Our take...

This story often appears as "proof" of 9/11 foreknowledge, despite its obvious problems.

If Ashcroft stopped flying by any commercial flights from July, for instance, then whoever "warned" him clearly had no detailed knowledge of the 9/11 plan.

What’s more, CBS only brought this issue up because it was normal for Government officials to fly commercial.

All other Bush Cabinet appointees, with the exception of Interior and Energy with remote sites to oversee, fly commercial airliners.
http://www.cbsnews.com/stories/2001/07/26/national/main303601.shtml

So if we’re to take the conspiracy slant on this story, then presumably we’re to believe that someone at the FBI knew something of 9/11. In which case why would they warn Ashcroft and no-one else? 

Something else you won’t read on most sites is Ashcroft’s own response to this, before the 9/11 Commission:

BEN-VENISTE: ...At some point in the spring or summer of 2001, around the time of this heightened threat alert, you apparently began to use a private chartered jet plane, changing from your use of commercial aircraft on grounds, our staff is informed, of an FBI threat assessment. And, indeed, as you told us, on September 11th itself you were on a chartered jet at the time of the attack.

Can you supply the details, sir, regarding the threat which caused you to change from commercial to private leased jet?

ASHCROFT: ...Let me indicate to you that I never ceased to use commercial aircraft for my personal travel.

ASHCROFT: My wife traveled to Germany and back in August. My wife and I traveled to Washington, D.C., on the 3rd of September before the 17th -- before the 11th attack on commercial aircraft.

I have exclusively traveled on commercial aircraft for my personal travel; continued through the year 2000, through the entirety of the threat period to the nation.

The assessment made by the security team and the Department of Justice was made early in the year. It was not related to a terrorism threat as a threat to the nation. It was related to an assessment of the security for the attorney general, given his responsibilities and the job that he undertakes. And it related to the maintenance of arms and other things by individuals who travel with the attorney general. And it was their assessment that we would be best served to use government aircraft.

These were not private chartered jet aircraft. These were aircraft of the United States government. And it was on such an aircraft that I was on my way to an event in Milwaukee on the morning of September the 11th.
http://www.nj.com/war/ledger/index.ssf?/news/ledger/stories/20040414_ashcroft.html

Of course anyone who’s going to believe Ashcroft would willingly leave others in danger to keep himself safe, probably won’t have a problem assuming he’s lying here. But the thing is, he’s not alone. Even the team behind Michael Moores Farenheit 9/11 believe the “stopped flying commercial flights” story isn't entirely true.

As proof of its scrupulousness, the Moore [Fahrenheit 9/11] team cites adjustments it made to the film's portrayal of Attorney General John Ashcroft...

An earlier version of the film... included a reference to a widely circulated charge, broadcast by CBS News in July 2001, that Mr. Ashcroft had received warning of threats and stopped flying on commercial airlines. Tia Lessin, supervising producer of "Fahrenheit 9/11," said the reference to the CBS report was cut after Mr. Moore's fact-checking team found evidence that Mr. Ashcroft had flown commercially at least twice that summer.
http://www.nytimes.com/2004/06/20/movies/20SHEN.html?pagewanted=all&ei=5007&en=906cd89473ac07fc&ex=1403064000

So even Michael Moore (not exactly a friend of Bush, or Ashcroft) accepts there's probably nothing here? Then unless more information appears, this story really doesn't look like it's going anywhere.