The speed of electromagnetic waves in air is very close to the speed of light in a vacuum, which is approximately:

299,792,458 meters per second (m/s)

This is often rounded to 3 x 10^8 m/s for easier calculations.

While air does have a slightly higher refractive index than a vacuum, the difference is very small, so the speed of electromagnetic waves in air is practically the same as in a vacuum.