Another suggestion was put forward: could the loud noises in Colorado have been caused by military jets breaking the sound barrier? When planes go supersonic, they create shock waves, which sound a lot like an explosion on the ground below. Maybe this was the reason for the booms on that Monday night?
But a little more digging proved that that wasn’t it, either. Spears called the nearest place jets could have come from to find out more. All of the planes from Buckley Air Force Base were back on the ground by just gone 8:00 p.m. that night. And that was well before the residents of Denver began to report hearing the explosions in the sky.