That's a great point, I was curious so I looked it up. Google offered the following:
"The speed of light in air is about 299,705 kilometers per second, or 2.99705 × 10^8 meters per second. This is almost as fast as light travels in a vacuum, slowing down by only three ten-thousandths of the speed of light."
So seems like the speed of light in atmosphere is still a lot faster than fiber.
