A retired US Air Force sergeant has been arrested on charges of conspiracy to commit espionage.
Mr Brian P Regan was detained as he passed through a security checkpoint to fly to Zurich.
He is scheduled for an initial appearance in federal court in Alexandria, Virginia later today.
His luggage was searched at the airport, as was his Maryland home and car.
Authorities have not named the country he has allegedly spied for or what information he allegedly leaked.
After he retired from the Air Force in August 2000, Mr Regan worked for a US government contractor and was assigned to the National Reconnaissance Office in nearby Chantilly, Virginia, where he had access to classified information.
The case is being investigated by the FBI's Washington field office foreign intelligence squad.
The arrest follows the conviction of former FBI agent Robert Hanssen, a counter-intelligence expert who pleaded guilty to spying for Russian over 15 years.
PA