"They were planning massive attacks," Federal Prosecutor Monika Harms said.
"As possible targets ... the suspects named discotheques and pubs and airports frequented by Americans with a view to detonating explosives loaded in cars and killing or injuring many people," Harms told a news conference on Wednesday.
The suspects, two Germans aged 22 and 29 and a 29-year-old Turk, received terrorist training in Pakistan and had close ties to al Qaeda, according to Jorg Ziercke, president of Germany''s Federal Criminal Investigation Office.
Ziercke said the group was united by a "hatred against American citizens" as it planned attacks against Frankfurt airport, a popular international travel hub, and Ramstein air base, a major transit point for the U.S. military into the Middle East and Central Asia.
Harms said the group had amassed 680 kg (1,500 pounds) of hydrogen peroxide to make bombs that would have been among the biggest yet on German soil. Possible scenarios would have been car bombings used in simultaneous attacks.