Windows in several high-rises were reportedly damaged Friday during practice flights for the Chicago Air and Water Show over the weekend. The U.S. Air Force Thunderbirds were rehearsing their aerial demonstration when two distinct booms were heard by residents along Lake Shore Drive, prompting speculation that the jets had gone supersonic.

“Those were clearly sonic booms,” Matthew Clarke, an assistant professor of aerospace engineering at the University of Illinois Urbana-Champaign, told the Chicago Sun-Times after reviewing video of the incident. “Even though the global flow may not be faster than the speed of sound, there are places locally faster than the speed of sound, creating shock waves. While I can’t say that the whole plane went supersonic, I can say — from the video — shock wav

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