The U.S. Air Force denies its Thunderbirds went supersonic while practicing for the Chicago Air and Water Show on Friday, despite two blasts heard across the North Side that possibly shattered several windows in Lake View.

But videos of the F-16 jets show an obvious sonic boom, according to one aeronautics professor.

“Those were clearly sonic booms,” Matthew Clarke, assistant professor at the University of Illinois Urbana-Champaign’s Grainger College of Engineering, told the Sun-Times.

It is possible that part of a plane, and not the whole aircraft, exceeded the speed of sound to create shock waves that can be perceived as booms, Clarke said. This is possible when lift is created by air going over the wing, Clarke said.

“Even though the global flow may not be faster than the speed of s

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