Prosecutors are expected to decide at a high-level meeting today to seek a retrial of seven men on allegations of involvement in an al-Qaeda plot to attack transatlantic airliners.

Sir Ken Macdonald, QC, the Director of Public Prosecutions, will chair the meeting, which will also be attended by Peter Wright, QC, who presented the Crown case at the five-month trial at Woolwich Crown Court.

There was “disbelief” and “astonishment” among investigators when the jury returned its verdicts on Monday, revealing that it was not convinced of the existence of a plan to attack aircraft in mid-flight.

The Crown Prosecution Service and Scotland Yard had been confident that they had a compelling case that proved a terrorist conspiracy.

The evidence included six “suicide videos” that were allegedly intended to be released to the media after an attack, a mass of bombmaking material and extensive surveillance video and audio recordings.

Before the trial, defence lawyers were pessimistic about the strength of their cases. However, the jurors returned mixed verdicts against the eight defendants.

One Whitehall source described the outcome of the case as “Britain's O.J. Simpson verdict — unexpected and unpredictable”.

Three men — Ahmed Abdulla Ali, Assad Sarwar and Tanvir Hussain — were convicted of conspiracy to murder but the jurors were unable to agree whether their plan had been to detonate liquid bombs on passenger flights between London and North America. Sentencing has been adjourned until a later date.

The jury was also unable to reach verdicts on four other men — Umar Islam, Waheed Zaman, Arafat Waheed Khan and Ibrahim Savant — accused of being part of the murder conspiracy. They, however, had pleaded guilty to causing a public nuisance by recording “martyrdom videos” that they claimed were hoaxes.

Mohammed Gulzar, the eighth defendant, who was described by the Crown as the key link between the British plotters and Pakistani terrorists, was acquitted of all charges. He cannot be retried.

The review of the case is focusing increasingly on the management of the trial by Mr Justice Calvert Smith.

There is disquiet that the judge allowed the jurors a two-week holiday after they had retired to consider their verdicts. They were also given time off for one juror to attend a training course and they had several days off for illness. Between July 28, when the jury retired, and September 8, when it returned its verdicts, it deliberated for just over 56 hours.

One source close to the case told The Times: “I think the judge made a serious error by giving the jury a holiday after the evidence had concluded and they had started their deliberations. Was that a jury that was really concentrating solely on the evidence in the case? This is a huge case, with a vast amount of evidence. I think the public interest now demands that there is a retrial.”

Police and Whitehall sources discounted claims that the case had been undermined by the decision of the Pakistani authorities, under pressure from the United States, to arrest a leading figure in the plot.

The detention of Rashid Rauf on August 9, 2006, forced British police to bring forward their plans for arresting suspects here. Michael Chertoff, the US Homeland Security Secretary, had pushed for Rauf's arrest because of concerns over the threat to American cities.

One senior Whitehall official said: “There was a difference of view between the US and Britain over when to bring the investigation to a close.”

Police sources said, however, that the hurried arrests did not adversely affect the quality of evidence they were able to obtain. One added: “There wasn't a problem. We felt the evidence we had was overwhelming.”

In the first 48 hours after the arrests, police uncovered a “treasure trove” of evidence that they believed proved the existence of a big terrorist enterprise and would secure convictions. MI5 is still following leads to see if anyone else might have been involved on the periphery of the plot.

Rauf, the man whose arrest in Pakistan prompted the raids in Britain, escaped from custody and has not been seen or heard of since.

As lawyers considered a retrial, Virgin Atlantic became the first airline to call for a review of continuing security restrictions on carrying liquids in hand luggage. Paul Charles, the airline's director of communications, said that people were confused by different restrictions in different airports.

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