A number of figures closely involved in the Troubles in Northern Ireland - and subsequently the peace process - quickly observed the reasoning and type of human characteristics that led the aircraft hijackers to their targets in the US.
Terms like "symbolism" and "symbolism of the act" cropped up along with a number of phrases that would have been more familiar to the newspaper readers of the 1970s and 1980s when Islamic terrorism against the West was previously at its height.
One figure said the suicide bombers, in the last hours of their lives, are driven by an adrenalin rush. Studies into suicide bombers do refer to them becoming euphoric before their deaths. Any person who had been close to a terrorist attack in which death was imminent for either their target or themselves would have some recognition of this condition, he said.
The type of conditioning that organisations use on recruits to prepare them to risk - or lose - their lives is also familiar to many members of terrorist groups in Northern Ireland. The indoctrination process begins while the "volunteers" are pre-teen.
Here, the traditional induction method began with membership of the junior wing of the main terrorist organisations. The junior wings have different names so as not to scare candidates. In the IRA's case the junior wing is Fianna na h╔ireann; in the UVF' s case it is the Young Citizen Volunteers; in the UDA's it is the Ulster Young Militants.
The intensity of this conditioning increases as the members are inducted into junior paramilitary groups for weapons training. Gradually they move towards the point where they are brought on a mission involving the killing or injuring of a target. Security force people refer to this as the "blooding" process.
The reactions of the recruits to being placed in acts of terror are closely scrutinised by their seniors. Terrorist group commanders can quickly identify the type of person who would be able to carry out a murder, or mass murder involving their own suicide.
Some of those involved in the attacks on the World Trade Centre and the Pentagon may have been part of the Palestinian intifada in Israel or in other Islamic conflicts and worked their way up the selection process to the point where they were chosen for "martyrdom".
No group in Northern Ireland trains members for suicide missions. But all have had members who are prepared to risk their lives to carry out attacks. The IRA and INLA have come closest to sending people on suicide missions and both had such strong motivation that 10 of their members (seven IRA and three INLA) were prepared to die on hunger strike in 1981.
Thomas Begley, the young Catholic Ardoyne man walked into Frizzell's fish shop on the Shankill Road on October 23rd 1993 and detonated a bomb killing himself and nine Protestants. He was not a suicide bomber but died because the timer on the bomb was set to only a few seconds. He was almost certainly unaware of this. But still, Begley would have undergone an induction and conditioning process in the IRA that many Islamic terrorists would recognise.
The IRA may not have used suicide bombers but made others become de facto suicide bombers. This occurred during the period that became known as "human bomb". Its first victim was Patsy Gillespie, a Derry man who worked in the kitchen of a British Army. Gillespie's family was held hostage and he was forced to drive a van laden with explosives to the Army checkpoint outside Derry on October 24th, 1990.
The bomb exploded as he arrived, killing him and five soldiers. At first it was suspected that Gillespie had been strapped to the driver's seat of the van. However, it later emerged that he was warned that if he did not comply, the IRA would murder his family.
Gillespie was lulled into a false sense of safety by the placing of a clock with wires attached, that gave the impression he had plenty of time to spare when he reached the checkpoint. The clock was a dupe. The real trigger mechanism for the bomb was built into the switch in the door panel which normally turns on the cabin light. When Gillespie arrived at the checkpoint he immediately tried to get out to warn the soldiers. As he did this he set off the bomb.
"Martyrdom" plays a major part in the culture and ethos of most terrorist groups. The IRA and its offshoots dedicate a great deal of effort to commemorating their dead. Monuments to IRA members killed in the Troubles have sprung up all around the North in recent years. It can be taken as a given that new young recruits to the IRA are still lectured on the "sacrifices" of their predecessors. This year's 20th anniversary commemorations of the Maze hunger strikes will have been widely used to induct and condition recruits.
Anniversary is another important factor in terrorist thinking.
That the Twin Towers and Pentagon were struck on September 11th was no coincidence.
September 11th is the anniversary of the signing of the British Mandate in Palestine in 1922 which laid the constitutional foundations for the creation of the State of Israel.
This date was so heavily marked by Palestinian and other Islamic attacks on Israel and its main sponsor, the US, that a group emerged in the 1970s known as Black September.
On September 12th, 1970, this group blew up three airliners at Dawson's Field, Jordan. The signing of the Oslo peace accords between Israel and the PLO took place on September 13th, 1993. Another commemorative event in September is the massacre of Palestinian refugees at Sabra and Chatilla camps in Beirut by Israel's Lebanese Christian allies on September 16th, 1982.
Abu Nidal, the extreme Palestinian figure who is on the suspect lists being compiled by Western security agencies of the attacks in the US, hijacked a Pan Am Jumbo in the Pakistan city of Karachi in September 1985.
Every terrorist attack is first considered for its "symbolic" worth. Like the attackers of the World Trade Centre, the IRA chose to launch its biggest ever bomb attacks against the City of London in 1993 when it bombed the Baltic Exchange and Bishopsgate, and later Canary Wharf. Unionists, particularly the independent, Mr Robert McCartney, have argued that it is fear of a repetition of these attacks, which caused vastly expensive damage, that has led the British Government to "placate" the IRA.
An added incentive to Islamic terrorists attacking the World Trade Centre is that these are among the greatest symbols of Western financial interests and under strict Islamic teaching the charging of interest - which is referred to as usury - is prohibited.
Attacks on financial symbols like this are appreciated among the remaining Marxists who still inhabit core positions in many of the world's terrorist groups. Abu Nidal, for instance, comes from an extreme leftist background and would have once been strongly anti-Islamic. However, his group has since forged alliances with the extreme Islamic groups like Mr Osama bin Laden's Al Qa-ida.
Similarly, within the IRA leadership there are still avowedly left-wingers and even Marxists - hence its relationship with groups like FARC in Colombia. One of the IRA's top figures is Marxist. The organisation's political leadership has stated that its objective is the creation of a "32-country socialist republic".
Ironically a number of loyalist or unionist figures have pointed out this week that Mr bin Laden and the IRA have something else in common. Both were supported and financed by either the US administration or US supporters. In Mr bin Laden's case, he was part of the Mujahdeen movement that fought Russian occupation of Afghanistan between 1980 and 1988 during which time the US administration supported it.