The only medium through which light would travel faster than in air is a vacuum. In a vacuum, which is a space devoid of matter, light travels at its maximum speed, which is approximately 299,792,458 meters per second in a vacuum, often rounded to 3 x 10^8 meters per second for simplicity.
When light travels through a medium, such as air, water, or glass, it interacts with the atoms or molecules of that medium. These interactions can cause the light to slow down, resulting in a lower speed than its maximum velocity in a vacuum. The extent to which light slows down in a medium depends on the optical properties of the material, including its refractive index.
In comparison, in a vacuum, there are no atoms or molecules to interact with, so light can propagate without any obstructions or delays. Thus, light travels at its maximum speed in a vacuum, making it the only medium through which light would travel even faster than it does in air or any other material.