The US alleges the Meyerses spied for Cuba for decades
A retired US State Department employee and his wife, who are charged with spying for Cuba, have been denied bail by a court in Washington DC.
US Magistrate John Facciola deemed the pair, both in their 70s, a flight risk after prosecutors showed they were planning a Caribbean sailing holiday.
Walter Kendall Myers and his wife are accused of having passed on information to Cuba for three decades.
The pair deny the charges but face up to 20 years in prison if found guilty.
Defence lawyers had argued that the pair should be fitted with monitoring devices and allowed to return home to be with their children, the Associated Press news agency reported.
But prosecutor Michael Harvey told Judge Facciola that the couple, who own a yacht, were "plainly a serious flight risk" and should remain in jail until their court date.
He said a calendar in their home showed a date marked as the start of a sailing trip, with no return date indicated.
Investigators also found sailing charts for Cuban waters in the home, AP quoted Mr Harvey as saying.
Fidel Castro has dismissed the allegations as "ridiculous"
Mr Harvey said that if the couple were able to reach Cuba, they would present "a real and present danger to the United States".
"The Myerses would be greeted as heroes there. They would not be coming back," he said.
Defence lawyer Thomas Green did not comment as he left the courtroom but said his team would "keep plugging along".
The couple's arrest followed a sting operation by the FBI, in which an agent posing as a Cuban spy persuaded the couple to give him information about their activities.
During a subsequent meeting, Mr and Mrs Myers agreed to provide information about US government personnel to the undercover agent, the affidavit alleges.
They also made statements about their past activities for the Cuban government, it says.
Former Cuban leader Fidel Castro said he had met the couple in 1995, but has dismissed the allegations against them as a "ridiculous tale".