(L to R) Tanvir Hussain, Abdulla Ahmed Ali and Assad Sarwar were found guilty
Al-Qaeda is likely to try again to use aircraft to attack the West, Whitehall officials have told the BBC.
Security correspondent Frank Gardner said they believed the airline bomb plot was part of al-Qaeda's "obsession" with using commercial airliners.
The warning comes after three British men were convicted of plotting to blow up flights from London to North America using bombs disguised as soft drinks.
Defence expert Michael Clarke agreed that al-Qaeda was "still plotting".
On Monday, Abdulla Ahmed Ali, 28, Tanvir Hussain, 28, and Assad Sarwar, 29, were found guilty at Woolwich Crown Court after the UK's largest ever counter-terrorism operation
Their arrests in 2006 changed the face of air travel, prompting the introduction of restrictions on the carriage of liquids.
UK intelligence officers believe the plot was directed by al-Qaeda figures in Pakistan, including a British man - Rashid Rauf - from Birmingham, now thought to be dead.
Daniel Sandford, home affairs correspondent
Essentially, the rules in British courts are that you cannot use intercept material as evidence in a trial - except in very exceptional circumstances.
There has been a lot of pressure already to start introducing it - particularly in terrorism trials where people may have been detained or kept under control orders because of such evidence.
In the first airline trial the jury were deadlocked, but in the second trial when these fascinating e-mails communicating between the plot's leaders and Pakistan were introduced, there was no such deadlock.
These e-mails were not intercepted - they were taken off the Yahoo server in America - but it shows, people are saying, that intercept-type evidence works.
Prof Clarke, director of defence think tank the Royal United Services Institute, told BBC Radio 4's Today programme that al-Qaeda was more "marginalised" now than in the past, but still posed a threat to the West.
"There's no doubt there are people in the tribal areas on the border of Pakistan and Afghanistan who have tried these plots," he said.
"There were four or five big plots and they've all come to light in the UK. They haven't worked, but they're still plotting."
Commercial airliners, he said, were also "very soft targets", adding: "If it's possible to get a bomb onto an airliner then it's a goner."
Sajjan Gohel, from think tank the Asia-Pacific Foundation, said: "If the group [al-Qaeda] can't target the US directly it will go after its allies, namely the UK.
"Also it can tap in to the very large Pakistani diaspora inside the [UK] - many of whom travel to Pakistan where al-Qaeda is based - whom it can recruit, train, radicalise and send back to the UK."
Earlier, John McDowell, head of the Metropolitan Police's Counter Terrorism Command, said security staff and police were racing against time when they foiled the plot.
He told the BBC the arrest of the men was "a relatively close thing".
"It's always a balancing act to try to acquire the necessary evidence while at the same time ensuring that public safety is your most important consideration," he said.
"So, we ran this as long as we could run it as a covert, proactive operation and we moved in at the time that we felt that the risks were too great."
The operation also had to be speeded up after alleged US pressure led to the arrest of Rauf in 2006.
Michael Chertoff, former US Homeland Securities Secretary, said Rauf "was the individual involved in essentially supervising the plot, although he was not someone who was going to take part in the actual attack itself".
Former US security chief Michael Chertoff's reaction
The case has reinforced calls for the use of intercepted phone calls and e-mails as evidence in court.
The prosecution case included a series e-mails linking Ali and Sarwar with jihadist figures in Pakistan.
These were not intercepted - they came from the Yahoo server in the US - but the BBC's home affairs correspondent Daniel Sandford said they had given ammunition to those calling for intercept evidence to be used in British courts.
At present, phone tap and intercepted email evidence is not admissible, but Sir Ken Macdonald, who was head of the Crown Prosecution Service when the airline plot was uncovered, says the case is proof that a change in the law is needed.
"This is the best evidence you can have - people convicting themselves out of their own mouths," Sir Ken told the BBC.
At the time of his arrest, ringleader Ahmed Ali had identified seven US and Canada-bound flights to be blown up over the Atlantic within a two-and-a-half-hour period.
Airline terror plot: The evidence
Abdulla Ahmed Ali, Tanvir Hussain and Assad Sarwar were arrested in August 2006. They were each accused of two charges of conspiracy to murder using home-made explosives.
All three were found guilty in an earlier trial of conspiracy to murder involving liquid bombs - but that jury could not decide whether their plans extended to detonating the devices on planes.
Now a second jury has decided that such a terror plot did exist.
The prosecution alleged that the three ringleaders planned to explode home-made bombs disguised as soft drinks on seven trans-Atlantic flights from London's Heathrow airport.
1. 1415 UA931 LHR-SAN FRANCISCO (United Airlines)
2. 1500 AC849 LHR-TORONTO (Air Canada)
3. 1515 AC865 LHR-MONTREAL (Air Canada)
4. 1540 UA959 LHR-CHICAGO (United Airlines)
5. 1620 UA925 LHR-WASHINGTON (United Airlines)
6. 1635 AA131 LHR-NEW YORK (American Airlines)
7. 1650 AA91 LHR-CHICAGO (American Airlines)
During their investigation police found equipment that could have been used to make bombs in King's Wood, High Wycombe, and in Forest Road, east London. Assad Sarwar, the quartermaster, bought a suitcase to store bomb parts in the woods near to his home. There, he hid bottles of hydrogen peroxide, also known as hair bleach. This chemical was the key ingredient for the home-made bombs.
At the bomb factory in east London, the ringleaders experimented with the design of their devices which were to be disguised as soft drink bottles. The small bombs would then be smuggled in hand luggage through airport security.
The theory of bomb construction is detailed above, but precise details shown to jurors have been omitted.
This video simulates the damage caused by a liquid bomb to a commercial airliner. The BBC used a qualified explosives engineer, Sidney Alford, to construct the devices to demonstrate their likely effect on an aircraft fuselage.
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