FBI agents and San Jose police spent several hours questioning a Santa Cruz man Wednesday after a fellow passenger on a Frontier Airlines jet from Denver glimpsed ``suicide bomber'' written on the man's journal.

Convinced the man wasn't part of terrorist plot, authorities then set him free.

``Whatever the person wrote in their journal was not against the law,'' police spokesman Enrique Garcia said.

But the writing was enough to alarm a passenger who notified a crew member on Flight 169 about 40 minutes after take-off that the man was acting bizarrely, writing in his journal and clutching his backpack.

Authorities boarded the plane and escorted the 36-year-old man off the jet after it landed safely at Mineta San Jose International Airport with 112 passengers aboard.

The legal distinction between writing the words ``suicide bomber'' and saying it aloud on a plane is all about ``context,'' said Special Agent LaRae K. Quy, spokeswoman for the FBI's San Francisco office.

If someone shouted ``bomb,'' Quy said, authorities would be able to quickly discern the intent.

But written words aren't so obvious. For example, authorities would have to determine who wrote the offending words and parse its meaning, she said.