John O. Brennan, the president’s chief counter-terrorism adviser, said that American authorities now believe the two bombs, fashioned from printer toner cartridges, found inside cargo packages on Friday were designed to blow up an airplane carrying them, despite being addressed to Chicago synagogues. “We’re looking at the potential that they would have been detonated en route to those synagogues aboard the aircraft, as well as at the destinations,” he said on Face the Nation this morning. “But at this point we would agree with the British that it looks as though they were designed to be detonated in flight. It is my understanding that these devices did not need somebody to detonate them.” One of the bombs traveled on two passenger planes within the Middle East — from Yemen to Qatar, and then Qatar to Dubai — before arriving at the Dubai airport where it was discovered. The second bomb was found while traveling on a UPS plane in England.