Investigators think only one or two trainees had contact with Masri. Trainees had autonomy to instruct and supervise a dozen fellow militants back in Britain, officials say. In turn, investigators believe Masri got direction from his bosses, who often communicate with the command structure through messengers.
"We have patchy intelligence on the relationship and structure between external operations figures and Zawahiri and Bin Laden," the senior British official said. "In the really big plots, we think they played a role."
Investigators monitored the plotters for months, managing to film inside their London safe house. In August 2006, police rounded them up. The attack was weeks away and would have targeted five planes, the U.S. anti-terrorism official said.
Three months later, Pakistani helicopter gunships blew up a remote madrasa, killing about 80 people but missing Masri, officials say. In late 2006, however, Israeli, Turkish and U.S. spies teamed up to capture Hadi, the former Iraqi military officer, in Turkey as he was en route to Iraq to improve relations with the Al Qaeda offshoot there, officials say.
Masri assumed more control. He allegedly turned his aim to another part of Europe he knows. Last spring, he taught bomb-making in compounds in North Waziristan to aspiring suicide attackers, including a 21-year-old Pakistani living in Denmark and a 45-year-old Pakistani-German, according to U.S. and European officials.
A U.S. anti-terrorism source sees Masri's role as a symptom of decline. "The fact he trained them himself shows you some of the limitations of the network," the source said.
In any case, Masri's pupils apparently displayed more fervor than stealth. Aided by U.S. intercepts of communications to Pakistan, Danish police put the 21-year-old under surveillance along with his associates, one of whom had been in Pakistan at the same time. As in London, police got deep inside the alleged cell, U.S. and European officials say.
Police installed clandestine cameras and microphones in the 21-year-old's apartment in a scruffy area that mixes immigrant families and young Danes. In early September, the cameras filmed the 21-year-old and an Afghan suspect as they sang militant songs and mixed TATP, the explosive used in the London attacks. The two even conducted tests of detonators in a vestibule, officials say.
