Tests by government scientists, played to the jury, produced videos of the devices producing an explosion powerful enough to punch a hole in an aircraft fuselage.

The Crown believed it had overwhelming evidence. Six of the men recorded suicide videos making threats against the west, which the prosecution said would have been released after the planes were blown up in mid-air.

The security service MI5 had captured incriminating statements with covert listening and video devices planted in the east London flat which the cell used as a bomb factory.

US and UK intelligence believe the cell was directed by al-Qaida leaders in Pakistan.

Liquid explosives were to have been hidden in Lucozade and other soft drinks bottles. Disposable cameras would have been used to help set off the devices which would also contain regular batteries, hollowed out to contain chemicals.

In their defence, Ali and Sarwar said they planned to record a documentary highlighting injustices against Muslims in Iraq, Afghanistan and Lebanon.

Ali said he considered exploding a small device at the Houses of Parliament or Heathrow’s terminal three as a publicity stunt to draw attention to the programme.

He claimed martyrdom videos recorded by six of the defendants were a hoax to be used as part of the internet documentary to make it more shocking.

In April while opening its case, the Crown played videos of Ali found after his arrest. In it he warned of “body parts … decorating the streets” if Muslims were not left alone, and said he had yearned to take part in violent jihad since he was a teenager. In the martyrdom video he is seen speaking against the backdrop of a black flag with Arabic writing on it. Last night the CPS said: “The prosecution is considering the request for a retrial in respect of the plot to blow up airliners against all seven men upon which the jury could not agree.”

The home secretary, Jacqui Smith, said: “I am indebted to the police and security services who, by successfully disrupting this group, have saved countless lives. I would also thank the Crown Prosecution Service, which has worked tirelessly to ensure that these individuals have been brought to justice. I am sure they will now consider what to do where no verdict was reached.”

The trial judge, David Calvert-Smith, excused the jurors from any further service for the rest of their lives and offered his appreciation. “Depart this court with the full-hearted thanks of the community for your service to it, which is far beyond the duty for most jurors, and my personal thanks,” he told them.