Edward Snowden's whereabouts unknown

An empty passenger seat believed to be reserved by former US spy agency contractor Edward Snowden is seen on a plane to Cuba in Moscow's Sheremetyevo airport, June 24, 2013. Russia defied White House pressure on Monday to expel Snowden to the United States before he flees Moscow on the next stop of his globe-crossing escape from US prosecution. [Photo/Agencies]

A plane en route to Cuba takes off from Moscow's Sheremetyevo airport, June 24, 2013. There was no sign that former US spy agency contractor Edward Snowden was onboard a Russian plane bound for Cuba as it prepared to take off on Monday, a Reuters correspondent on the plane said. A flight attendant said Snowden was not on the plane and the seat he had been expected to occupy was taken by another passenger. [Photo/Agencies]