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. One such flight landed Tuesday evening, another leaves this 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.

On Tuesday, Bolivia — backed by Nicaragua, Ecuador and Venezuela — called the move against Morales’ plane an “act of aggression” and called on the Organization of American States to approve a declaration demanding that such an incident never be repeated. But while officials in Italy, Spain and France have backed away from embracing what took place — France called it a “technical” error, and Italy and Spain have denied they barred Morales’ jet — the lesson is clear.

“I would think it’s very instructive and worrisome for Snowden,” said a U.S. aviation expert, speaking on condition of anonymity because of the high political sensitivities surrounding the case. “Those states were on absolutely firm legal ground to deny (Morales) use of their airspace. Politically? That’s a judgment call.”

The aviation expert said flights fall into two main categories. The first is civil, such as most commercial and charter airlines, as well as postal services such as FedEx. The other category is state flights, which would cover military, police and aircraft such as Morales’ or President Obama’s Air Force One that are used by governments.

Going the state flight option would require one of the Latin American countries to send a government plane and arrange for diplomatic clearance all along the way — a long shot with no ironclad guarantee of safe passage for Snowden.

If Snowden takes a regularly scheduled commercial flight out of Moscow, any country it flies over could order it to land.

And finding a path that doesn’t overfly a U.S.-friendly country is nearly impossible. A blogger for The Washington Post made a stab at coming up with such routes this week, including one that would carry Snowden to Iran and then Africa. All the routes were dubious and risky, the blogger concluded.

“He’s in a pickle,” the aviation expert said, adding that he couldn’t recall a similar case in his long career in the industry. “He’d want to be sure that every country he’s flying over or refueling in wouldn’t arrest him.”

And lurking under all the problems with air travel is another logistical kink: Snowden’s lack of travel documents. His U.S. passport was revoked, so it’s unclear how he’d be processed out of Moscow. In other asylum cases, those not involving fugitives accused of revealing state secrets, refugees have traveled on specially issued United Nations passports, or other temporary documents issued by individual countries.

One factor in his favor, analysts say, however, is the shrewd way Snowden appears to be using his revelations in his case for sanctuary. While governments might expect and forgive the United States for its global surveillance dragnet, ordinary people all over the world have expressed outrage at the program’s scope and targets.

Snowden has leaked damning information about the U.S. spying on China, the European Union and Latin American nations — all places that are instrumental to his safe passage. In deciding whether to ground a plane that might be carrying Snowden, experts said, nations would have to weigh bilateral relations with the United States against the folk-hero status Snowden enjoys among many of their own citizens.

“Everyone wants plausible deniability,” said David Gomez, a former FBI assistant special agent-in-charge and counterterrorism program manager who retired recently after nearly three decades at the agency. “The other nations might assist us, but nobody wants the award for helping us nab Snowden.”