Almost seven years after terrorists hijacked airliners and used them as missiles to kill 2,973 people, five men who allegedly plotted the attacks face a military tribunal Thursday.

Khalid Sheikh Mohammed, the alleged September 11 mastermind, is seen shortly after his capture during a raid in Pakistan in this file photo from March 1, 2003 in this photo obtained by the Associated Press. Mohammed, who could face the death penalty for his role in the September 11 attacks, has been peppering his military lawyer with questions in advance of his war crimes trial at Guantanamo, the attorney tells The Associated Press. [Agencies]

Khalid Sheikh Mohammed, the confessed mastermind of the September 11 attacks, will be arraigned simultaneously with four other detainees inside a high-security courthouse at the remote US Navy base in Guantanamo Bay, Cuba.

Mohammed boasted of numerous attacks and plots against the United States in a closed military hearing last year, and the al-Qaida kingpin and his confederates will be given the chance to speak out again in their war crimes trial, according to a top tribunal official, Air Force Brig. Gen. Tom Hartmann.

"In the course of trial they'll have opportunity to present their case, any way they want to present it subject to rules and procedures," Hartmann said, "That's a great freedom and a great protection we are providing to them. We think ... it is the American way."