The group will pay €400 million for the remaining 80% of the company following the conversion of a €100 million loan into a 20% equity stake in the carrier last summer.
The move comes, IAG said, to boost the organisation’s growth opportunities in the Latin America and Caribbean market.
Luis Gallego, IAG chief executive, said the agreement will enable IAG’s Madrid hub to compete on an "equal footing" with other European hubs and consolidate its position in the south Atlantic.