"A direct flight on an aircraft is also subject to the head and tailwinds involved for the routing, that would shorten the possible range," he noted. But: "The longest range private jet currently on the market is the Gulfstream G550, with a direct range of 6750 nautical miles." Other more common aircraft have shorter ranges. The Boeing Business Jet can go 6,141 nautical miles, for example.
Update, July 9: An emailer notes that this data is outdated. The Bombardier Global 8000 can travel 7,900 nautical miles.
Twidell also pointed out that, by law, private aircraft have to land with fuel on board, in case the aircraft needs to divert from its intended destination in an emergency, somewhat shrinking the range under normal conditions. But we'll set that aside for our purposes. (He also noted that commercial aircraft, bigger and carrying more fuel, routinely fly much farther. A regular flight between Newark and Singapore in an Airbus A340 covers 8,200 nautical miles.)
Which brings us to the question of where he can go. We've updated our map showing countries to which he's applied for asylum; it appears below. Black indicates a country that has rejected an asylum claim; yellow, a pending one; green, a country that has indicated some level of support.
Based on this, we narrowed the possibilities down to four: Iceland, Bolivia, Venezuela, and Cuba. (Update: We added Venezuela.) Why not China? Snowden has had better opportunities to get to China, but didn't avail himself of them.
Using Google Earth's handy distance calculation tool, we looked at the distances between Snowden's current location and the airports near the capital cities of each country in an effort to figure out how far that private plane would have to fly.
Reykjavik, Iceland: 2,210 nautical miles
In each of the ensuing maps, you'll notice that we assumed the same route: north from Moscow, past the eastern edge of Finland, but outside its territorial control, along the northern edge of Norway. Russia has a lot of coastline, but for travel west, which all of these scenarios require, it's by far the fastest way.
In the case of Iceland, the next stretch of the flight is simple. Snowden's plane could simply continue on to Reykjavik, landing safely well within the plane's operational distance.
Sucre, Bolivia: No can do
Unfortunately for Snowden, Bolivia turns out not to be an option. Completely land-locked, there's no way that his plane could make it to the country without passing through another nation. Not to mention that it's by far the longest flight of all of the options.
Caracas, Venezuela: 6,017 nautical miles
This flight is a little trickier than the one to Iceland. First of all, it's much longer. Second, it requires navigating the small Caribbean islands just off the Venezuelan coast. (That red dot furthest to the west in that image represents that avoidance.) In all, though, manageable.