American Alan Gross has been released from a Cuban prison after five years in a surprise move that could pave the way for a major shift in US policy toward the communist island nation.
The 65-year-old was on an American government plane bound for the US after being released on humanitarian grounds by the Cuban government at the request of the Obama administration.
As part of the secret negotiations to secure his release, the US was releasing three Cuban jailed in Florida for spying.
Obama administration officials have considered Mr Gross's imprisonment an impediment to improving relations with Cuba.
President Barack Obama is due to address the nation on Cuba, the White House said, and US officials said he was expected to announce Mr Gross's release.
Bonnie Rubinstein, Mr Gross's sister, heard the news from a cousin, who saw it on television.
"We're like screaming and jumping up and down," she said in a brief telephone interview from her home in Texas.
Mr Gross was detained in December 2009 while working to set up Internet access as a subcontractor for the US government's Agency for International Development, which does work promoting democracy in the communist country.
It was his fifth trip to Cuba to work with Jewish communities on setting up Internet access that bypassed local censorship.
Cuba considers USAID's programmes illegal attempts by the US to undermine its government, and Mr Gross was tried and sentenced to 15 years in prison.
The three Cubans released in exchange for Gross are part of the so-called Cuban Five - a group of men who were part of the Wasp Network sent by Cuba's then-President Fidel Castro to spy in South Florida.
The men, who are hailed as heroes in Cuba, were convicted in 2001 in Miami on charges including conspiracy and failure to register as foreign agents in the US.
Two of the Cuban Five were previously released after finishing their sentences.