The top speed of a fighter jet with its afterburners on can vary depending on the specific aircraft model and its design. Many modern fighter jets are capable of reaching supersonic speeds, which means they can fly faster than the speed of sound.

The speed of sound in air at sea level and at a temperature of around 20 degrees Celsius (68 degrees Fahrenheit) is approximately 343 meters per second (about 1,125 feet per second). This speed is often referred to as “Mach 1.”

Fighter jets, when using their afterburners, can achieve speeds greater than Mach 1, typically in the range of Mach 2 (twice the speed of sound) or even higher. Some of the fastest fighter jets in the world, such as the F-22 Raptor and the F-15 Eagle, are capable of reaching speeds exceeding Mach 2.

It’s important to note that the speed of sound varies with factors like air temperature and altitude. At higher altitudes and in colder air, the speed of sound is lower, so supersonic speeds in those conditions may not be as high in terms of meters per second, but they would still be described as Mach numbers greater than 1.

In summary, the top speed of a fighter jet with afterburners on is significantly faster than the speed of sound, and it is typically measured in terms of Mach numbers to indicate how many times the aircraft’s speed exceeds the speed of sound in a given air environment.