In normal air, how fast do EM waves travel?

air does not affect the speed of light at 3x10e8 m/s

Air slows the speed of light, but insignificantly so.

I think you could still use 2.98 x 10^8 metres per second.

At the speed of light, 299,792,458 metres per second which is approx 186,000 miles per second. Air offers no resistance to EM radiation, the speed is the same in a vacuum.

Just shy of the speed of light in a vacuum. Air has a refractive index of about 1.0003 at standard temperature and pressure, so there's little variation.

The speed of light in vacuum is 299,792,458 m/s.

The speed of light when it passes through a transparent or translucent material medium, like glass or air, is less than its speed in free space. The speed is inversely proportional to the refractive index of the medium.

The speed of light in air is only slightly less than c (the refractive index of air is only slightly larger than one: about 1.000292). Therefore, speed of light in air is 1/1.000292 of c, or approximately 299,704,944 m/s