According to authorities, Harris began his latest trip in China, where he purchased a one-way ticket to Korea.
In Korea, he purchased the ticket that took him through Japan to LAX. His final destination was to be Boston, authorities said.
The China ticket information did not appear in a federal affidavit on the case because that leg of the trip wasn't immediately apparent from the U.S.-bound ticket authorities first found in Harris' possession.
Harris, when detained, was questioned by a series of detectives before invoking his right to counsel. Officials described him as savvy and closed.
Harris only made his one potentially relevant statement -- "almost like he was talking to himself" -- when he relaxed during an interview with one detective who had a family member that had the same last name as his mother's maiden name, sources said.
Though he was arrested Friday, because of the federal holiday Harris made his initial appearance Tuesday in a Los Angeles federal court and remained in federal custody. Harris was scheduled to be back in court Friday for a detention hearing.
The FBI, according to officials, has notified its legal attaches in both China and Japan of the troubling materials they found with Harris, the pornographic pictures and writings on his computer and the concerns given his close proximity to children in his teaching role.
The FBI asked its counterparts to look into a number of areas and advised them of Harris' interest in pornography and fantasy rape in the hope that it might provide additional avenues for investigation.
The Department of Homeland Security and the Transportation Security Administration also are looking into the matter and how it could have been avoided.
"TSA will review, in concert with aviation security officials in Korea, how a prohibited item was able to travel in checked baggage and implement any necessary changes," DHS Director of Communications Matt Chandler said.
Harris came to the United States as a child, was raised in the Boston area and attended Boston University. He had an interest in science, investigators said, and calculations or formulas were found in a diary in his possession.
Harris was being represented by criminal defense attorney Steven A. Seiden, who is also representing the controversial anti-Islam filmmaker Nakoula Basseley Nakoula.
Reached for comment, Seiden's office described Harris as a highly intelligent and diligent student who attended excellent schools in Boston and has no criminal history or violent tendencies.
"I will speak about Mr. Harris on Friday when I know more about Mr. Harris and what I might say at that time," Seiden said Wednesday. "Thank you."
ABC News' Michael S. James, Matt Hosford and Erin Keohane contributed to this report.