http://flightaware.com/live/flight/AFL150/history/20130707/2...
http://flightaware.com/live/flight/AFL150/history/20130702/2...
http://flightaware.com/live/flight/AFL150/history/20130701/2...
All of those nearly miss US airspace. This flight just happens to miss it a bit more.
Today's Aeroflot 150 does not follow a great circle route, modified or otherwise. Such a deviation has nothing to do with weather or other environmental factors and can only be explained by a need to avoid a particular airspace and the potential for diversion to an alternate airport within that airspace in case of an emergency.
You will notice that the route overflies the Azores, Bermuda and Nassau so that those airports, rather than airports in continental North America, can be used as alternates when filing the flight plan.
This is the most telling aspect of the diversion, even more so than the diversion from the great circle.
Someone important who needs to avoid the airspace over North America at all costs is on that plane.
With this: http://flightaware.com/live/flight/AFL150/history/20130707/2...
What you see is a substantial deviation from one to the other. One flies over land in the US quite a bit, the other only very briefly.
If headwinds are bad enough on the great circle route it could actually be more efficient to take a non-great-circle route. Airplanes fly relative to the air, not the ground. So if the air is moving fast enough in the wrong direction it can lengthen the route substantially. The jetstream can be more than 100mph. http://en.wikipedia.org/wiki/Jet_stream
EDIT: It's also not terribly wise to state something as fact (that I am wrong) when neither of us will know either way until the media reports on it. We can both speculate, but unless we know the pilots on the airplane and they confided in us prior to the flight, we can't know. I don't know the pilots and I suspect that you don't either. So let's not dress up guesswork as facts.
One correction: upon looking again at FlightAware, it is clear that the flight specifically avoided controlled airspace around the Azores, probably because Portugal has strenuously declined to allow overflights that may have certain passengers aboard.
Edit: I mean you are wrong about "happens to miss", that's all. Planning air routes is not a matter of happenstance, and all of the examples you have given run counter to your argument, because they prove that Moscow-Havana flights invariably follow a great circle or a modified great circle route. If you can show me any previous AF150 that follows a flight path that resembles today's flight path, I will concede the point.
https://flightaware.com/live/flight/AFL150/history/20130620/...
https://flightaware.com/live/flight/AFL150/history/20130608/...
Today's flight started out on a much mores southerly route, overflying Belrus, Poland, the Czech Republic, Germany, Luxembourg, Belgium and France, but avoiding Spain, Portugal and the Azores.
Thank-you for the information. I am probably wrong. We'll see.
In fact if you click on the track log they all say "Estimated" at all their points.
I'm not saying Snowden is or is not on the flight. Just that getting all excited about a route deviation might be a bit premature given that there isn't a hard rule about where you're supposed to fly.