In the early days of air travel, planes faced a problem. The tips of their propellers were going faster than the speed of sound, and there was a risk that they could become unstable and rip apart in the air. That left engineers with a question: was it possible for a plane to fly at supersonic speeds without disintegrating? What about for a pilot to fly that fast? They created a plane to test their theory, and made the sky their laboratory. Hear about the exciting test in the video below.