It is hard to believe that once upon a time aircraft were unable to travel faster than the speed of sound. It was viewed as impossible to pass that kind of speed, hence where the term “sound barrier” came from. The ability to break the sound barrier into supersonic speeds actually came from a very simple engineering trick allowing aircraft to reach that speed.
In simple terms, there was one simple trick in the engineering of an aircraft that let aircraft reach supersonic speeds, sweep the wings. When wings are in a straight, fixed position they don’t allow air to properly flow creating too much resistance. However, in the swept position they can reduce the drag while continuing to accelerate through transonic speeds into supersonic speeds.
“On a straight wing airplane, all of the airflow over the wing travels parallel to the aircraft’s chord line. But, on a swept wing, only some of the air flows parallel to the chord line. The other part flows perpendicular to the chord – this is called spanwise flow.”
Fairly simple if you understand the science and engineering behind all of it. But if you don’t understand it then check out this video from Seeker explaining the process.