Three young British Muslims who were turned into bombers while doing charity work in Pakistan are facing life behind bars after being convicted of plotting mass murder.

Abdulla Ahmed Ali, Assad Sarwar and Tanvir Hussain were accused of conspiring to bring down at least seven transatlantic airliners in mid-air, using bombs hidden in soft drinks bottles.

The plot brought chaos to Heathrow and led to new global security procedures preventing passengers taking liquids through security in airports.

And police believe that, although 13 people were arrested over the plot, there are still five members of the cell at large.

Yesterday, after 56 hours of deliberations and a four-month trial at Woolwich Crown Court, a jury found the three men guilty of conspiracy to murder.

But in a blow to Scotland Yard and the Crown Prosecution Service, none of the alleged conspirators was convicted of a separate murder charge directly linking the liquid bombs to an attempt to blow up aircraft.

The jurors also failed to reach verdicts on four other alleged members of the terrorist cell – all young British Muslims from London and Buckinghamshire.

All seven admitted plotting to cause a public nuisance. An eighth man, Mohammed Gulzar, who was claimed by prosecutors to have flown into Britain to supervise the final stages of the plot on the orders of al-Qa'ida, was cleared of all charges.

Ali, 27, and Sarwar, the "quartermaster" of the cell, were radicalised as volunteers for a British Islamic charity in a Pakistani camp which housed thousands of refugees displaced by the US-led invasion of Afghanistan.

The two men travelled to the Chaman refugee camp close to Pakistan's border in 2002, claiming they were volunteers for the Midlands-based Islamic Medical Association (IMA) and were deeply affected by their work tending the injuries of children fatally wounded by US bombs.

The CPS last night defended itself against claims that the jury had rejected the airline bomb plot and said it was considering a retrial of the seven men, excluding Mr Gulzar, on the charge.

Operation Overt, which began early in 2006, was one of the largest conducted by Scotland Yard and the biggest peacetime surveillance operation, involving officers from MI5, the Metropolitan Police and other forces around the country.

The trial heard that the men used equipment from grocery and hardware shops, and a hairdressing wholesaler to build weapons to cause "death on an almost unprecedented scale".

Ali, from Walthamstow, north-east London, received training in how to conduct the plot during repeated visits to Pakistan and its lawless border area with Afghanistan between 2000 and 2005 before creating the bombs with Sarwar's assistance.

It can now be revealed that Ali was in contact with the mastermind of the failed 21 July bombings. Muktar Said Ibrahim called Ali in 2004 and officials believe they may have met in Pakistan between December 2004 and May 2005. The visits coincided with the presence in Pakistan of two 7 July conspirators, Mohammad Sidique Khan and Shahzad Tanweer. All three groups planned terror assaults using bombs based on hydrogen peroxide.

In a "suicide" video recorded by Ali, he referred to Osama bin Laden, saying: "Sheikh Osama warned you many times to leave our lands or you will be destroyed and now the time has come for you to be destroyed. And you have nothing to expect other than floods of martyr operations."

Sarwar, from High Wycombe, Buckinghamshire, and Hussain, 27, were key figures, used for buying the equipment needed to made the liquid explosive – fashioned from a powdered soft drink mixture and hydrogen peroxide hair bleach – and a second more powerful explosive to be used as a detonator. The bombs were to be disguised in 500ml Lucozade and Oasis bottles.

A bug in Ali's flat revealed it had been converted into a bomb factory and used to record "suicide" videos with the other alleged conspirators. Early potential targets included Canary Wharf and oil terminals.

The jury was unable to reach verdicts on conspiracy to murder charges relating to four other defendants –Ibrahim Savant, Arafat Khan, Waheed Zaman and Umar Islam.