WASHINGTON -- Beginning a third week holed up in a Moscow airport’s transit zone, Edward Snowden finds himself far enough away to evade U.S. authorities, but also too far from any of the sympathetic nations willing to shelter him.

Aviation experts say that even if Snowden accepts the tentative offers of Venezuela, Nicaragua or Bolivia to give him shelter, it’s virtually impossible to chart a flight plan to those nations that doesn’t include traveling over or refueling in a U.S.-friendly country that could demand inspection of the plane – and detain him.

Nations have full, exclusive jurisdiction over their airspace, so any plane carrying Snowden could be forced to land if it flies over the territory of a country that’s willing to help American authorities capture the fugitive intelligence contractor. Snowden faces felony charges in the United States for leaking classified documents that detailed the National Security Agency’s extensive surveillance apparatus.

“Nations control their airspace up to the heavens, the old saying goes,” said John Q. Mulligan, an aviation law expert at DePaul University’s College of Law. “Just look at the map. It’s probably possible to figure out a route that wouldn’t touch the airspace of the United States or any friendly nations, but it wouldn’t be easy.”

Snowden’s best hope for breaking out of the transit area most likely hinges on whether he could sneak onto one of five weekly, direct flights to Havana, Cuba. One such flight landed Tuesday evening, another leaves Thursday afternoon. The main drawback? The path takes the plane directly over the United States, which could flout a standing treaty and force a regularly scheduled commercial flight to land.

There are airplanes that can make the 6,000-mile direct flight from Moscow to Havana or Caracas with fuel to spare. The Airbus A340 has a range of about 9,000 miles and a Boeing 777 can fly for 9,400 miles before refueling. But a direct flight would mean passing through the airspace of European nations and possibly the United States. And chartering such a craft would be incredibly expensive – $100,000 to start, and that’s if a charter service could be found willing to risk angering the United States and perhaps being accused of aiding a fugitive.

“I don’t know what sort of plane they’d have available to make that flight, especially without refueling,” Mulligan said. “A refueling stop would probably be problematic for Snowden.”

While President Barack Obama has said he wouldn’t be “scrambling jets” to haul in Snowden, the U.S. government has shown that it can pressure countries that would serve as pit stops for Snowden on his way to Latin America or other potential exile destinations. Snowden has petitioned more than 25 countries for asylum; the State Department has promised “grave difficulties” for bilateral relations with any nation that aids his escape.

Last week’s diversion of Bolivian President Evo Morales’ presidential jet as he attempted to return to Bolivia from Moscow was a cautionary tale for Snowden as he mulls exit strategies from transit-lounge limbo. France, Spain, Italy and Portugal denied Morales’ requests to overfly their airspace on the way to a refueling stop in the Canary Islands.

The president’s plane was rerouted to Austria and spent 14 hours there, touching off a diplomatic firestorm that may have made some Latin American nations even more willing to play host to Snowden, but also showed the limitations of their ability to help him.