Britain remains under "immense threat" from international terrorism which can only be defeated by global cooperation and solidarity among all ethnic groups in the country, Home Secretary John Reid said Friday. Reid, speaking a day after British anti-terror police said it foiled a wave of suicide attacks on US-bound aircraft, made a point of thanking Pakistan for its "vital" intelligence operation. He said that seven people had been arrested in Pakistan in connection with the plot. While the investigations and police operation against the suspects were "driven" by Britain, Pakistan had provided vital intelligence clues, Reid told a news conference in London. "We are very grateful for all the help and cooperation from our international partners, including Pakistan," said Reid. But he stressed that the police operations against suspects in Britain were "ongoing" and that the threat remained "immense." He confirmed that Britain remained on the highest level of terrorist alert, according to a report of the German News Agency "DPA." Meanwhile, the Evening Standard newspaper reported Friday that the terrorist plotters had earmarked August 16 as the day for their multiple mid-air attacks on aircraft. "The plotters set 16/8 as the date they would bring down 10 packed passenger jets bound for the US with liquid peroxide-based bombs," the paper said. Air tickets to fly out on a United Airlines flight next Wednesday had been found at the home of one of the people arrested, said the Standard. There was to be a "practice run" attempt to board a US-bound airliner Friday, for which tickets had also been found. Reid refused to give details of the ongoing police investigations, but confirmed that 24 people were in custody. Most are believed to be British-born Muslims with connections to Pakistan.