By Miguel Lo Bianco

BUENOS AIRES Argentine officials on Monday welcomed the return of an airplane from which the country's last military dictatorship threw political opponents to their deaths, and that will now be part of a museum dedicated to the victims' memory.

The turboprop plane took part in the so-called "death flights" that Argentina's bloody 1976-1983 dictatorship employed as one of its tools to get rid of critics.

The victims on one flight on Dec. 14, 1977, included French nuns Alice Domon and Leonie Duquet, who had spoken out about the growing number of "disappeared" people during the dictatorship.

Another victim, Azucena Villaflor, had helped start the Madres de Plaza de Mayo, a group of mothers dedicated to searching for and seeking justice for their disappeared children, before she herself was detained and killed by the dictatorship.

"It is terrible to think that a mother who was only looking for her son was thrown alive from this plane," her daughter Cecila told Reuters.

At the request of relatives of the victims, Argentina's economy minister bought the plane and organized its transfer from the United States.

It will be housed at a museum in the capital, Buenos Aires, on the site of a former clandestine detention and torture center where death flight victims were held before their murders.

"The past cannot be changed, but it does serve to learn from it," Vice President Cristina Fernandez de Kirchner said on Monday during a ceremony presenting the airplane.

The event was attended by relatives of the victims, Fernandez de Kirchner, and Sergio Massa, economy minister and presidential candidate for the ruling party, who led international efforts to recover the aircraft.

The Skyvan PA-51 was identified in 2010 by journalist and survivor of the dictatorship, Miriam Lewin, and the Italian photographer Giancarlo Ceraudo, using flight logs.

The discovery provided evidence used in a historic trial that convicted dozens of people of dictatorship-era crimes.

About 30,000 people disappeared during the 1976-1983 dictatorship, according to human rights organizations.

(Reporting by Miguel Lo Bianco; Writing by Lucila Sigal and Brendan O'Boyle. Editing by Gerry Doyle)