The speed of light in air is:

The speed of light in air is slightly less than the speed of light in a vacuum. When light moves through air, it encounters a medium that is denser than a vacuum. This interaction slows it down, but only by a very small margin. In a vacuum, light travels at approximately 299,792,458 meters per second. In the air, it travels at about 299,702,547 meters per second.

This difference means the speed of light in air is approximately 1.0003 times slower than its speed in a vacuum. While this change may seem significant at first glance, it is only a minor reduction, representing about 89,911 meters per second less than the vacuum speed. Despite this reduction, the speed of light in air remains extremely fast, with its value typically rounded to roughly 3 × 10⁸ meters per second.

To summarize, the speed of light in air is very close to its maximum value in a vacuum, and it slows down only slightly due to the medium it passes through. This demonstrates how the properties of air affect the speed of light in air, but the difference is so minor that it is often negligible for most practical purposes.