From The Blotter:
According to a Department of Homeland Security briefing to the aviation sector, the terrorists appear to have planned to use multiple persons aboard each flight to assemble peroxide-based liquid or gel high explosives. The bomb-making materials could easily be concealed in small containers — water bottles, tooth paste tubes, juice boxes and any of the other numerous person items passengers traditionally take into the passenger compartment of commercial flights.At least nine transcontinental flights from American, United and Continental airlines were targeted in the plot. ABC News has learned that terrorists planned to attack the planes three at a time, waiting an hour between each attack.
According to federal authorities, two or three bombers would each carry a separate portion of the bomb onto the plane to avoid detection. Once onboard the bomb would be assembled and then detonated by using heat or friction.
British authorities had been tracking some of the suspects for several weeks but stepped in to round up the plotters when they began to book flight reservations.