They have also revealed parts of an e-mail they say Richard Reid sent to his mother two days before he boarded the Paris to Miami flight in which he defended his planned actions, calling himself a warrior against "oppressive" US forces in Muslim countries.
The glimpse of the case being built against Mr Reid, 28, came as the FBI asked the US District Court in Boston to continue restrictions on defence lawyers discussing publicly what their client has told them.
They believe Mr Reid is part of Osama Bin Laden's al-Qaeda network and could use statements to pass hidden messages to groups planning attacks on the US.
Mr Reid denies charges of attempted murder, attempted homicide and attempted use of a weapon of mass destruction.
He was arrested in 22 December after being overpowered on American Airlines flight 63 while allegedly trying to ignite explosives concealed in his shoes. The flight was diverted to Boston.
Forensic evidence
In documents filed with the court, prosecutors said forensic tests on a human hair and a palm print found inside the device did not belong to Mr Reid, indicating that at least one other person had helped him.
"(The) investigation since 22 December has established that Reid was not unassisted in his efforts to destroy Flight 63, and that his choice of a target was a deliberate and calculated act of international terrorism," government lawyers wrote.
Mr Reid's lawyers have not commented on the statements.
Prosecutors also noted that Mr Reid - who had no known source of income - made journeys between July and December 2001 that took him from Belgium to Israel, Egypt, Turkey and Pakistan.
In the e-mail message which prosecutors say Mr Reid sent to his mother, he told her not to be upset with his actions because "what I am doing is part of the ongoing war between Islam and disbelief".
Charges against Mr Reid
Attempted use of weapon of mass destruction
Attempted murder
Attempted homicide
Placing an explosive device on an aircraft
Interfering with a flight crew (two counts)
Attempted destruction of an aircraft
Using a destructive device
Attempted wrecking of a mass transportation vehicle
The e-mail says: "I see it as a duty upon me to help remove the oppressive American forces from the Muslim land and that this is the only way for us to do so as we do not have other means to fight them."
Prosecutors hope their latest submissions will persuade the Boston court not to lift the restrictions on Mr Reid's lawyers.
The trial is scheduled to go ahead in November and the next hearing is due on 3 June.
Mr Reid faces a maximum life sentence in prison if convicted.
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