Supersonic aircraft are designed to travel at speeds that exceed the speed of sound, which is approximately 343 meters per second (1,235 kilometers per hour or 767 miles per hour) at sea level. The speed of sound, also known as Mach 1, can vary with altitude and atmospheric conditions. When an aircraft surpasses this speed, it is referred to as supersonic. These aircraft have various applications, including commercial travel, reducing flight times significantly, and military uses, offering strategic advantages due to their speed. Examples of supersonic aircraft include the Concorde, which was used for commercial flights, and military jets like the F-22 Raptor. The development and use of supersonic aircraft involve complex engineering challenges, particularly concerning noise (sonic booms), fuel efficiency, and environmental impact. Therefore, the correct answer to the given question is; option [C] at more than the speed of sound.