Its scope was ruthlessly ambitious, causing destruction that police say would have been unimaginable.
The alleged plot to destroy several US-bound planes with liquid explosives appears to bear the fingerprints of al-Qaeda.
Counter-terrorism officials say that the plot may even have been "the Big One" that they have been dreading ever since September 11, 2001, particularly as the fifth anniversary of 9/11 approaches.
More than 20 people have been arrested, terror threat levels have been raised to their highest levels in Britain and America, and thousands of flights have been cancelled worldwide.
Prof Paul Wilkinson of the Centre for the Study of Terrorism and Political Violence (CSTPV) at St Andrews University said nothing on this apparent scale had succeeded before.
“This is really a very ambitious plot indeed, it is the kind of spectacular potentially lethal attack which the al-Qaeda network has been particularly interested in carrying out,” he said.
“I would be very surprised if it was found that they were not involved as a movement. It is possible, I suppose, that some other movement could have copied the kind of techniques that had been used by the al-Qaeda network but I think that’s unlikely."
Rohan Gunaratna, a terrorism expert at Singapore’s Institute of Defense and Strategic Studies, agreed, saying that everything known so far points to involvement by Osama bin Laden’s terror group.
"It is a classic al-Qaeda tactic. It is a hallmark of al-Qaeda to carry out coordinated, simultaneous attacks, and the aviation domain is certainly known to al-Qaeda. They have obvious experience in working around that system and extensive knowledge of the aviation domain."
Michael Chertoff, the US Homeland Security Secretary, echoed those sentiments, saying the planned attack "was sophisticated, it had a lot of members and it was international in scope". He added that: "It was in some respects suggestive of an al-Qaeda plot," but before anyone jumped to conclusions he warned that the investigation was still under way.
There have been dozens of thwarted plots around the world since 2001, and several that were murderously successful.
Suicide bombers killed 52 people in London on July 7 last year, 58 died in two attacks in Istanbul in 2003, and 202 were murdered in Bali in 2002. Islamic radicals killed 191 people in Madrid on March 11, 2004, then the main suspects for the plot blew themselves up days later as police were closing in.
While al-Qaeda’s call for global jihad clearly acted as inspiration, there has been no direct evidence that Bin Laden or his No 2, Ayman al-Zawahiri, had advance knowledge of those attacks, that they helped plan them, or that they provided financial or logistical help to those who carried them out.
The group’s failure to match the destruction it inflicted on 9/11 has led to speculation that a global dragnet that has forced Bin Laden into hiding, and ensnared many of his most trusted deputies, may have degraded al-Qaeda’s abilities.
But analysts said today that that is a theory to be believed only at the world’s peril.
The airline plan had the potential to dwarf the attacks of recent years - killing hundreds, perhaps thousands. It also appears to have involved far more extensive planning and expertise.
Counterterrorism agents have been tracking the alleged plotters for months, and made arrests in London and the south-east of England, as well as Birmingham. Senior police sources said that the suspects appeared to be "homegrown", though it was not immediately clear if they were all British citizens.
Magnus Ranstorp, a terrorism expert at Sweden’s Centre for Asymmetric Threat Studies, who has done extensive research into al-Qaeda’s efforts to recruit in Europe, said the foiled plot in Britain could very well have been an attempt at ’the Big One'.
Andrea Nativi, a researcher at the Rome-based Military Centre for Strategic Studies, said that the London plot resembled that of September 11 in its ambition, and was an entirely different animal from other terror schemes of recent years.
"By comparison, the London subway attacks look like child’s play," he said. "The new element here is their cleverness in trying to overcome the new security systems installed after 2001... No one can really expect to pass security checks with explosives in their pocket, they had to look for a plan B."
Rodolfo Mendoza, a police intelligence official in the Philippines, said that the modus operandi was the same as al-Qaeda has used in the past - and he should know. Mendoza was among the law enforcement officers involved in thwarting a plot by al-Qaeda terror mastermind Ramzi Yousef as long ago as 1995 to use liquid explosives to blow up a dozen airliners as they flew across the Pacific Ocean to US destinations like Los Angeles, San Francisco, Honolulu and New York.
Like al-Qaeda’s decade-long effort to bring down the World Trade Center in New York, first in 1993 and then, disastrously, in 2001, the latest plot to blow up commercial airliners reveals the group’s unwavering resolve, Mendoza said.
"These people are obsessed," he said. "They will try and try and try again to accomplish their mission."
Peter Neumann, director of the Centre for Defence Studies at London’s King’s College university, said that the 1995 Bojinka plan involved blowing up 11 planes using nitroglycerine mixed in contact lens solution and a battery powered detonator hidden in a shoe.
Scenes at airports up and down Britain and the US today, as liquids were banned on board planes, and air passengers' shoes were searched, pointed to the fact that similar methods may have been involved in the plot uncovered today.
"This liquid explosive type of attack is particularly worrying," Mr Neumann told Reuters.
"Planes remain vulnerable and in the coming weeks terrorists will be thinking of something else to do that we have no idea about."
Prof Paul Wilkinson of the Centre for the Study of Terrorism and Political Violence (CSTPV) at St Andrews University said nothing on this apparent scale had succeeded before.
“This is really a very ambitious plot indeed, it is the kind of spectacular potentially lethal attack which the al-Qaeda network has been particularly interested in carrying out,” he said.
“I would be very surprised if it was found that they were not involved as a movement. It is possible, I suppose, that some other movement could have copied the kind of techniques that had been used by the al-Qaeda network but I think that’s unlikely."
