What actually happens when light encounters air? Let’s say a green laser is shone onto a target ten meters away. Suppose we look at a photon as it attempts to travel to the target. Please correct my assumptions as needed.
Assumptions:
1. It could get “lucky” and miss all of the nitrogen and oxygen atoms. In this case it would be essentially traveling in a vacuum and travel at the full speed of light.
2. It could hit an atom indirectly causing the photon to scatter or disperse and not reach the target.
3. It could hit either a nitrogen or oxygen atom directly transferring all of its energy to the atom, but due to the atom’s structure and the photon’s energy level a new photon is not emitted. I believe it takes at least a Ultraviolet photon to get a photon out of a nitrogen or oxygen atom.
The problem is there no event that simply slows the light to the refractive index air. What am I missing? It seems like all of the events either misdirect, stop or have no affect on the photon.
 A: So I am not a quantum field theorist. But what one would likely tell you is that at the single photon level, you need to think about the transmission "quantum mechanically".  That is, the photon has a wavefunction which travels all the possible paths from emitter to detector simultaneously. Add the complex amplitudes of each of these possibilities to determine what the photon actually does.  In this way, it interacts with all the atoms simultaneously. The coherent interference of all these interactions/paths gives you an effective ("dressed") photon which has all the properties of the original photon, except a somewhat shorter wavelength, larger momentum, and of course slower speed (more precisely, phase velocity) through the medium.  You can think of it like a mess of coherent absorptions and re-emissions that follow the "photon" and slow it down as it propagates to the detector.
In any case, be careful about how you're thinking of the "photon's" wave-like and particle-like properties. Because, if you simply imagine a photon like a little ball flying through space and maybe bumping into things, you'll run into conceptual difficulties. After all, what is a photon other than the transmission of a packet of energy and momentum from point A to point B, as dictated by the interference of a wavefunction? 
At least, that's how the QED formalism deals with it (I think). What is actually happening is a matter of interpretation. I personally like the transactional interpretation of quantum mechanics, and I'll leave it as an exercise for the reader to determine how TI would explain this photon transmission process. 
