An Algerian man with suspected al-Qaeda links has been jailed for six years for downloading information on how to blow up a passenger jet.
Police believe Abbas Boutrab is a false identity
Abbas Boutrab, 27, was arrested in Newtownabbey, near Belfast, over suspected immigration offences.
Police later found computer disks with downloaded bomb-making instructions. He had denied the terror charges.
He has been on remand in prison for two years and seven months and is expected to be released in April 2006.
When Boutrab was convicted last month, Crown Court judge Mr Justice Weatherup said the information could have been of use to terrorists.
He also said that modifications made to the circuitry on a cassette player indicated intent.
"I am satisfied that his possession of the material was not out of curiosity but was for terrorist purposes," the judge said.
The FBI built a bomb at a Virginia test centre using the instructions and illustrated the devastation it could cause on a plane.
At Tuesday's sentencing, the judge said Boutrab should be deported once he is released from prison in Northern Ireland.
"Now we find the terrorism threat is subsiding (in Northern Ireland) and a new threat is emerging," said the judge.
"This new threat has an added horror because the terrorist stands amongst the innocent men, women and children.
"That's a feature in the material that was recovered here. It provides instructions for improvised explosives with the objective of bringing down an aircraft and the lives of all those on board."
The FBI built a bomb using Boutrab's method and tested it
During the trial, the court heard computer discs containing instructions on how to make explosives for use on board aeroplanes, and how to carry out an attack, were found at his flat in the Whitehouse area of Whiteabbey.
Details on how to make a silencer for an assault rifle were also found as were a number of false identities and passports.
Boutrab was tried under the Diplock system, where a judge in a terrorist case sits without a jury.
Police have described him as "a very dangerous man", and said Abbas Boutrab was not his real name, but another assumed identity.
A senior detective said he remained "a determined terrorist who has become expert in the procurement and forging of false identities" and had "a strong allegiance to a terrorist group that is linked to the al-Qaeda network".
Police believed Boutrab had lived and operated throughout Europe and that the discovery of an international terrorist in Northern Ireland was "unusual."
Italian, Dutch, French and Irish police forces assisted the investigation along with the FBI and the UK's Security Service.