LONDON— Three men were convicted today of conspiracy to murder in a terrorist bombing campaign, but the jury could not reach a verdict on allegations they plotted to use liquid explosives to down trans-Atlantic airliners.

The jury failed to reach any verdict at all for four defendants, and one man was acquitted in a case that caused travel chaos in 2006 at the height of the summer vacation season. Prosecutors said they were considering a retrial.

Prosecutors said a group of British Muslims led by Abdulla Ahmed Ali planned to use explosive hydrogen peroxide disguised as a soft drink and considered national infrastructure targets including gas terminals, oil refineries and Heathrow Airport.

Prosecutors said during the trial that the men, all Britons with ties to Pakistan, planned to attack United Airlines, American Airlines, and Air Canada flights.

But the jury could not reach a verdict on prosecutors’ claims that Ali intended to target passenger jets flying from London to major North American cities with suicide attacks.

A jury in London found that Abdulla Ahmed Ali and coconspirators Assad Sarwar and Tanvir Hussain were guilty of conspiracy to murder by the use of hydrogen peroxide to make a bomb.

The jury failed to reach verdicts on charges against four other defendants — Ibrahim Savant, Arafat Waheed Khan, Waheed Zaman, and Umar Islam. An eighth man, Mohammed Gulzar, was acquitted.

The men’s plans were stopped by British and American intelligence officers in an investigation that led to a bomb factory in eastern London, British woodlands where chemicals had been dumped and to Japan, Mauritius, South Africa, and Pakistan’s lawless tribal areas where conversations were intercepted.

Police swooped down and arrested two dozen suspects in dawn raids across Britain on Aug. 10, 2006.

Airports in America and Europe ground to a halt with hundreds of flights canceled over security concerns. Planes were stuck on runways for hours. Tempers flared as passengers lined up to surrender carry-on items under new security precautions that restricted the quantity of liquids in their luggage.

A lawyer for Ali, the alleged ringleader of the group, insisted last month he was guilty only of planning a childish stunt to make a political point.

Ali acknowledged planning to release anti-Western videos and detonate explosives at a high-profile location as part of a campaign to change the British government’s policy toward the Muslim world.

“It was childish, it was stupid, but it is not murder,” the lawyer, Nadine Radford, said during a July hearing.

Ali, Sarwar, and Hussain had already pleaded guilty to conspiring to cause explosions. All eight denied conspiracy to murder.

Ali told the court they planned to set off a small bomb at a site such as the Houses of Parliament or Heathrow Airport to advertise a propaganda documentary protesting the West’s actions in Afghanistan and Iraq. He denied intending to kill anyone.

Ali, Sarwar, Hussain, and two others also have acknowledged conspiring to cause a public nuisance by distributing al Qaida-style videos threatening suicide bomb attacks at Britain. The three remaining defendants deny all charges.

Prosecutors say the cell was likely inspired by both the Sept. 11 attacks and the July 2005 London transit bombings, although they do not allege the men had direct links to al-Qaida.

Wright told the court that police found a computer memory stick in Ali’s pocket with details of flights from London’s Heathrow Airport to Chicago, New York, Boston, Denver, Miami, and Montreal.

Prosecutors also say the men had stockpiled enough hydrogen peroxide to create 20 liquid bombs, although they did not create any viable explosives, and no date had been chosen for the attacks.