Windalco's parent company UC Rusal has repaid US$371 million of debt to Russia's largest lender Sberbank ahead of schedule.
Rusal, the world's third largest aluminum producer, has increased focus on reducing its total debt, which was US$7.9 billion at the end of June.
It is also moving to modernise its assets.
That coincides with President Vladimir Putin's call for Russian exporters to invest more at home to help the coronavirus-hit economy.
Rusal still owes Sberbank US$2.1 billion and 79.5 billion roubles as part of the loan, which is due at the end of 2027 and is secured against part of Rusal's 25.5 percent stake in metals miner Nornickel.