An American startup company recently gave reporters a chance to see its first demonstrator aircraft, which is set to begin flight testing next year. The tests will be an important milestone for the company. It has plans to develop a passenger airplane that can travel faster than the speed of sound. The Colorado company, Boom Supersonic, showed off its XB-1 aircraft for the very first time last week. The model is designed for testing purposes only, not to carry passengers. Boom plans to begin test flights of the XB-1 next year. The company said the plane is the first supersonic jet to be independently developed. A handful of U.S. companies are exploring ways to restart supersonic passenger travel for the first time since 2003, when the Concorde stopped flying. The Concorde was a supersonic passenger jet operated jointly by Britain and France.