But as Ressam, 37, awaits sentencing Wednesday, prosecutors say he could have done more.
The government is seeking 35 years behind bars for Ressam. Prosecutors say he has stopped talking with investigators and consequently has jeopardized two related terrorism prosecutions.
Federal agents boosted security at the downtown U.S. District Court on Wednesday in advance of the hearing. Police buses were used to block off streets around the courthouse.
Ressam's public defenders are asking for 12½ years — and say Ressam is willing to continue cooperating but doesn't remember as much as he used to.
Ressam was arrested in Port Angeles in December 1999 as he drove off a ferry from British Columbia. He ran when Customs agents searched his car but was caught about six blocks away. In his trunk were explosives more powerful than TNT and digital watches that could be used as timers, authorities said.
Because Ressam had a one-night reservation for a motel just blocks from the Space Needle in Seattle, the mayor called off most of the city's celebrations to welcome the year 2000.
Also found in the car, authorities said, was a California tour book with Ressam's fingerprints on pages showing downtown Los Angeles and the Transamerica tower in San Francisco. In Ressam's apartment was a map with circles around Los Angeles International Airport, and two other California airports.