(Reuters) - Korean Air has completed its protracted purchase of indebted South Korean rival Asiana Airlines, the airline said on Thursday, a major step towards forming one of Asia's biggest carriers. The 1.8-trillion-won ($1.3 billion) M&A deal, which stands as one of the longest to completion in the sector, was first unveiled four years ago by South Korea's largest carrier to rescue Asiana, grappling with a plunge in demand during the COVID-19 pandemic. Korean Air acquired 131,578,947 newly issued shares in Asiana on Thursday, for a stake of 63.88% stake in the airline, which becomes a subsidiary. A new Korean Air group could account for just over half of South Korea's passenger capacity, and would become the world's twelfth-largest airline by international capacity, a Reuters analysis of airline data from Cirium and OAG shows. Korean Air said Asiana's integration would not include layoffs. "The combined organisation projects natural staff growth through business expansion, with employees in overlapping functions being reassigned within the organisation," it said in a statement.