The good news is that British authorities thwarted a plot to blow up in midair around 10 airliners en route to the United States from Britain. The bad news is that the incident shows that the threat of an indiscriminate terrorist attack remains, reminding us that no nation or community can let up on its vigilance.

The foiled plot, which led to the arrest of 24 Britons, occurred more than a year after subway and bus bombings killed 56 people in London on July 7, 2005, and nearly five years after the 9/11 attacks in the U.S. In March 2004, train bombings in Spain killed some 200 people. An attack on trains last month in India also killed about 200 people.

Twenty-two of the 24 arrested are British citizens of Pakistani origin, many of them apparently muslims. As with last year's London bombings, the latest case points to links between Pakistan, a haven for militant Islamists, and immigrant communities in Britain. Three of the four terrorists who blew themselves up in the London attacks were Muslims. A report by the British government and Parliament says the four were inspired by the al-Qaida terrorist organization and that two of them likely had contact with elements close to al-Qaida in Pakistan.