Russian airline Aeroflot has claimed that NSA whistleblower Edward Snowden is not on board its flight from Moscow to Cuba - despite earlier reports.
It had been believed that Snowden, who was in Moscow after leaving Hong Kong, was flying to Cuba to evade US efforts to extradite him.
But after the plane boarded, an Aeroflot agent claimed that Snowden was not on the plane.
Guardian journalist Miriam Elder tweeted: "Boarding is over. Aeroflot agent says Snowden not on plane.
"Aeroflot agent said they [passengers] are all Russians."
It was reported that 30 journalists had boarded the aircraft to interview the whistleblower. One of them tweeted a picture of an empty seat, said to have been reserved for Snowden.
The travel time of the SU150 flight is 12 hours and 40 minutes. Russian media reports suggest the Aeroflot aircraft will cross the Atlantic Ocean close to Newfoundland, believed to be under the jurisdiction of New York air traffic controllers.
If Snowden were on board, the US would have the "formal right" to intercept the plane when it passed through US airspace.
"No doubt, our US colleagues have the formal right to land the plan when it enters US airspace, which is their responsibility zone," a source at the Sheremetyevo airport in Moscow told the Interfax news agency.
"However, they will have to provide good reasons for [ordering the plane to land].
"The plane's captain has this right and he can change the course at his discretion. There should be enough fuel for that. As a rule, there is always some fuel reserve in planes."
The airlines had allegedly asked for the mobile phones of all the passengers on the flight and pledged to return them when the plane lands.