The US has said it will try to bring to trial a Lebanese hijacker freed last week by Germany after being in jail since 1989.
Mr Hammadi's release is 'disturbing', says victim's brother
Mohammed Ali Hammadi, 41, flew back to Beirut last week.
He was jailed for his part in killing a US Navy diver during the seizure of a TWA passenger jet in Beirut in 1985.
A State Department spokesman said the US was talking to Lebanese authorities about Mr Hammadi's extradition, but had no treaty with Lebanon.
"We have demonstrated over the years that when we believe an individual is responsible for the murder of innocent American civilians, that we will track them down and that we will bring them to justice in the United States," State Department spokesman Sean McCormack said.
'Served his time'
A spokeswoman for the German Justice Ministry told reporters that he had "served his time".
She said that the ministry had never received an extradition request from the US.
The brother of the murdered diver, Robert Dean Stethem, called Mr Hammadi's parole "absolutely disturbing".
The TWA plane - Flight 847- was hijacked between Athens and Rome
His mother Patricia said of Mr Hammadi: "We'll be after him. We won't let it rest."
TWA Flight 847 from Athens to Rome was hijacked on 14 June 1985, forced to land in Beirut. The plane's passengers were kept as hostages for 17 days as the aircraft flew between Beirut and Algeria twice.
The hijackers demanded the release of 17 members of Hezbollah and the Iraqi Islamic Daawa Party detained in Kuwait for attacks that killed six people in 1983.
During the incident, the hijackers killed US Navy diver Mr Stethem and dumped his body on to the runway apron at Beirut Airport.
Mr Hammadi was arrested at Frankfurt Airport in 1987 when he tried to smuggle liquid explosives into Germany.
Mr Hammadi's three accomplices in the hijacking - Hassan Izz-Al-Din, Ali Atwa and Imad Mughniyeh - are still at large.