Significant dates in the investigation of Zacarias Moussaoui, the French national accused of conspiracy in the Sept. 11 terror attacks:

Feb. 26-May 29, 2001: Moussaoui trains at Airman Flight School in Norman, Okla., where he reportedly is not a good student. School officials say that while most students are allowed to fly solo after 12 to 20 hours of lessons, Moussaoui was not allowed to fly alone after 57 hours. He leaves the school without a license.

Aug. 17: Moussaoui is detained on immigration concerns after arousing suspicions by seeking to buy time on a flight simulator for jetliners at a Minnesota flight school. While Moussaoui is in custody, federal agents attempt to get a search warrant for his computer. The request is denied by the Justice Department due to lack of evidence.

Sept. 11: Terrorists hijack four jetliners and crash them into the World Trade Center, the Pentagon and a field in Pennsylvania. At this time Moussaoui is still in custody. In the days following the attacks, Moussaoui is moved to New York and held as a material witness in the terror investigation. Authorities say he refuses to cooperate.

Dec. 11: A federal grand jury indicts Moussaoui on six conspiracy counts, four of which could carry a death sentence. It is the first indictment directly related to the attacks.

Dec. 19: Moussaoui makes his first appearance in federal court in Alexandria, Va., where he is ordered held without bail.

Jan. 2, 2002: Moussaoui is arraigned on the six-count indictment. He declines to enter a plea, prompting U.S. District Judge Leonie Brinkema to enter a not guilty plea on his behalf.

Jan. 18: Judge Brinkema denies a request by Moussaoui and several cable networks to televise the trial.

April 22: Moussaoui fires his court-appointed lawyers, claiming they are part of a conspiracy to execute him, and demands the right to represent himself with the help of a Muslim legal adviser.

June 13: Judge Brinkema grants Moussaoui the right to represent himself, keeping lawyers on standby to assist with his defense.

June 19: The government revises its indictment of Moussaoui.

June 25: During arraignment on the revised indictment, Moussaoui again refuses to enter a plea, then chooses a plea of "no contest." Judge Brinkema, suspecting Moussaoui's grasp of the law is shaky, refuses to accept the plea and enters a not guilty plea. She also denies Moussaoui's request to move the trial from Alexandria, near the damaged Pentagon.

July 16: Moussaoui is indicted a third time to allow prosecutors to specify conduct that would warrant the death penalty.

July 18: At his arraignment, Moussaoui attempts to plead guilty and declares his loyalty to Usama bin Laden. Judge Brinkema enters a not guilty plea, giving Moussaoui a week to change his mind.

July 25: Moussaoui pleads guilty to four counts of the indictment, then abruptly withdraws the plea after arguing with the judge.