An ex-naval officer from Argentina accused of killing political prisoners during the country's "Dirty War" has appeared in court in Spain.
The trial was suspended briefly as Mr Scilingo felt ill
Doctors who examined Adolfo Scilingo, 58, said he was fit to stand trial, despite having been on hunger strike.
Mr Scilingo is the first person to go before a Spanish court for crimes against humanity in another nation.
The former officer refused to answer the judge's questions on Friday and the trial was adjourned until Monday.
He is on trial in Spain as the country's law allows judges to try foreigners suspected of acts of genocide that have taken place outside Spain.
Mr Scilingo arrived at the national court in Madrid in an ambulance and suffered a dizzy spell in a holding cell, delaying the opening.
He sat in the courtroom wrapped in a blanket, slumped in his chair.
The session was interrupted by Mr Scilingo complaining of feeling ill, but resumed after doctors said he was fit to continue and was "aware of what he is doing".
One doctor told the court: "He is weak, but not enough to lose consciousness nor to have to be in a wheelchair."
Relatives of 'dirty war' victims protested outside the court
Mr Scilingo, sitting in a wheelchair, refused to answer the examining judge when asked whether he wanted to plead in relation to the charges against him.
Asked whether he knew why he was on trial, Mr Scilingo replied: "My head hurts."
The court did hear excerpts from comments Mr Scilingo made in 1997 to an investigating magistrate about his part in throwing 30 drugged, naked dissidents off airplanes into the Atlantic.
The presiding judge also read out the charges of genocide, which Mr Scilingo has denied, as well as 30 charges of murder, 93 of causing injury, 255 of terrorism and 286 of torture.
In 1995, Mr Scilingo told a journalist of so-called "death flights", during which drugged political prisoners would be stripped naked and flung, "one by one", out of aircraft flying over the ocean.
Mr Scilingo went to Spain in 1997 and was remanded for trial in 2001. He later retracted his account of the "death flights".
He has protested his innocence and went on hunger strike in December, recently refusing even to accept liquids.
Baltasar Garzon, the Spanish magistrate who brought the indictment, earlier sought to prosecute former Chilean dictator Augusto Pinochet under the same law.
Mr Garzon is spearheading a campaign to try officials linked to Latin America's military dictatorships for the death and disappearance of Spanish citizens abroad.
Between 10,000 and 30,000 people deemed to have been left-wing opponents of the Argentine regime were killed or vanished between 1976 and 1983.
Spain's national court in 1998 gave its judges the right to try anyone accused of crimes against humanity, even if the alleged crime took place outside Spain.