Mr. Harroun, who posted reports about his time in Syria on Facebook and YouTube, was charged in Alexandria, Va., with "conspiring to use a destructive device outside the United States," a crime that can carry a life sentence.
The soldier, Eric Harroun, 30, was arrested on Wednesday after arriving at Dulles International Airport outside Washington and charged in Alexandria, Va., on Thursday with "conspiring to use a destructive device outside the United States".
The day after the arrest, he was charged in the complaint with one count each of attempting acts of terrorism transcending national boundaries; attempted use of a weapon of mass destruction; using a destructive device in connection with an attempted crime of violence; transporting explosives; and attempting to destroy property with fire and explosives.
Mr. Shahzad was arrested on May 3 and charged in a criminal complaint with one count each of attempting acts of terrorism transcending national boundaries, attempted use of a weapon of mass destruction, using a destructive device in connection with an attempted crime of violence, transporting explosives and attempting to destroy property with fire and explosives.
In addition, he was accused of placing an explosive device on an aircraft, interfering with a flight crew, attempted destruction of an aircraft and using a destructive device during a crime of violence.
His plea also covered charges of attempted murder, two counts of interference with a flight crew and attendants, attempted destruction of an aircraft and using a destructive device during a crime of violence.
"I admit I used a destructive device," Mr. Reid said.
Mr. Barnes, 55, pleaded guilty in September to using a destructive device during a crime of violence and conspiracy to commit bank robbery.
When Judge Young asked whether he was pleading guilty to Count 8, "Using a destructive device during and in relation to a crime of violence," Mr. Reid sought to correct the judge.
He is also charged with one of count of arson causing great bodily injury and one count of using a destructive device and explosive to injure.
"I admit I used a destructive device in an act of war," he said, prompting Young to respond: "Very well". Raised by his mother in a small town west of London after his parents divorced, Reid embraced a youthful life of street crime.
