As Russian investigators piece together what happened in last week’s dual airline crash — now officially labeled as a terrorist act — U.S. officials, jittery over the intensifying campaign season, continue to scrutinize aviation activities. In Cleveland, Ohio, organizers are scrambling to get a waiver so they can go ahead with a planned air show this weekend after a stadium sports event was scheduled nearby. The FAA said that means no flying. If the show has to be cancelled, organizers said, the event is likely “doomed” for the future. Meanwhile, NORAD, the North American Aerospace Defense Command, is getting used to a post-9/11 reality — it may someday have to shoot down a passenger plane. “If we ever had to do that, the burden on the people who authorized the decision — they would never be the same,” said the head of intelligence for NORAD, who talked to the L.A. Times on the condition of “anonymity” (go figure). “Nor would the life of the fighter pilot who pulled the trigger.” And last week, the Department of Homeland Security announced it has awarded $90 million to two contractors to build and test prototypes to determine whether a viable technology exists that could be deployed to address the potential threat that shoulder-fired missiles pose to U.S. commercial aircraft.