LONDON — After two trials and the largest counterterrorism investigation in Britain’s history, three men were found guilty Monday of plotting to bomb at least seven trans-Atlantic airliners on a single day with liquid explosives smuggled aboard in soft-drink bottles and detonated by devices powered with AA batteries.

The convictions came three years after the global airline industry was thrown into chaos by the plot. The bombers’ plan to drain plastic soft-drink bottles with syringes and refill them with concentrated hydrogen peroxide, a bleaching agent also used as a propellant for rockets, led to new measures prohibiting passengers from carrying all but small quantities of liquids and creams onto flights.

The police and intelligence agencies in Britain and the United States had waited anxiously for verdicts in the six-month trial at Woolwich Crown Court in London, where eight men were accused of conspiracy to stage the airliner bombings.

Prosecutors said the plot could have killed at least 1,500 people aboard the targeted planes, which by that measure would have made it second only to the Sept. 11 attacks as the most serious terrorist plot in modern history.

The Obama administration praised the verdict.

“British authorities have worked diligently to investigate and prosecute those involved in the 2006 aviation plot,” Mike Hammer, a National Security Council spokesman, said in an e-mail message. “We congratulate them on those efforts and extend our thanks to the British government for seeing these efforts through to today’s conclusion.”

Last year, a trial in the case failed to bring verdicts. So the stakes were especially high in the second trial.

The jury found three men guilty of conspiring to kill passengers and crew members aboard the flights: Abdulla Ahmed Ali, 28, named by prosecutors as the plot’s ringleader; Tanvir Hussain, 28; and Assad Sarwar, 29, identified at the trial as the “quartermaster” of the plot, responsible for acquiring the explosives, detonators and other equipment and assembling them.

A total of eight men were in the dock during the trial. Four were found not guilty of plotting to bomb the planes. An eighth, Umar Islam, 31, was found guilty of conspiracy to commit murder.

The three men are due to be sentenced Monday.

After arrests in the liquid-explosives case were made in August 2006, documents found at the plotters’ homes and on a computer memory stick showed that they had earmarked airline schedules for seven flights leaving London for New York, Washington, Chicago, San Francisco, Montreal and Toronto. Evidence showed the plot aimed to detonate the bombs nearly simultaneously over the Atlantic.

The plotters’ intent, intelligence officials said, was to show that security measures adopted after Sept. 11 were insufficient to foil militants’ preferred low-technology, “asymmetric” attacks. All eight had pleaded innocent to most of the charges, saying they planned only a publicity stunt to raise awareness of Western policies in the Islamic world.

Evidence showed that several of the plotters, like those of Sept. 11, had traveled to Pakistan and Afghanistan for training by extremist groups linked to al Qaeda.

Though U.S. intelligence officials were deeply involved from the start because of the role that American electronic intercepts played in uncovering the plot, sources familiar with the trial said the case had divided the British and Americans from the beginning. U.S. officials had pressed for quick arrests of the terrorist cell involved in the plot, while the British sought to wait to gather more evidence in the hopes of winning more convictions.

(Source: Statesman.com / The Washington Post)