A federal court in Argentina has begun hearings in the largest trial for crimes committed under military rule, between 1976 and 1983.
Sixty-eight people face hundreds of charges of kidnapping, torturing and murdering mostly left-wing opponents of the military, the BBC reports.
A campaigner for justice, Carlos Pizzoni, says he hopes the trial will give answers for those who lost loved ones in the period.
Tens of thousands of Argentines were kidnapped and killed by the military junta during its years in power.
Among the defendants are Alfredo Astiz, known as the Blond Angel of Death, and eight former "death flight" pilots who allegedly took prisoners out to sea and dropped them from planes.
Tens of thousands of Argentines were kidnapped and killed by the military junta during their years in power.
The deadliest of the regime's secret detention camps was the Naval School of Mechanics (Esma) in the capital, Buenos Aires.
About 5000 people were sent to the grandiose three-storey stone building in an upmarket northern suburb.
Very few survived their time in cells in the basement and attic. The bodies of many have never been recovered.
A heart carved into the wall at the Naval School of Mechanics (Esma) A heart carved into the wall in a detention cell at the Naval School of Mechanics (Esma) where the crimes in this trial were committed
Some were allegedly burnt and their remains disposed of.
Others were drugged and dropped from planes flying over the Atlantic Ocean.
Among the alleged pilots of those "death flights" on trial is former naval lieutenant Julio Poch, who was extradited to Argentina from Spain in 2010 after allegedly confessing to the part he played to colleagues at the Dutch airline Transavia.
Another defendant, former naval captain Emir Sisul Hess, allegedly told relatives of the dead how sleeping victims "fell like little ants" from his plane.
The trial is part of a continuing series of actions against Argentine officers and other officials associated with the military dictatorship.
Legal action began once democracy returned to Argentina in 1983, but President Raul Alfonsin brought an end to the trials in 1986, arguing the country needed to look to the future and not the past.
Three laws granting amnesty for crimes committed during the Dirty War were passed in 1986 and 1987. These were overturned in 2003.
Since then a number of high-profile figures from the regime have been convicted, including the de facto presidents Jorge Videla and Reynaldo Bignone.
General Videla had already been convicted of homicide, torture and kidnap amongst other crimes in 1985, but he was given an amnesty by President Carlos Menem in 1990.
About 250 convictions have been secured, including Alfredo Astiz, who last year was given a life sentence for the part he played in infiltrating left-wing groups and betraying their members to the regime.
A number of Esma officials have already been tried but human rights lawyer Rodolfo Yanzon told the Associated Press: "This was, is and will be the largest trial of crimes against humanity.
"There are 68 defendants charged in 800 cases, and we estimate there will be some 900 witnesses,"
The trial is expected to last two years.