Qatar Airways said on Wednesday it had increased its holding in Aer Lingus-owner IAG to 25.1pc, buying another stake worth $600m (€555m) as part of a strategy it described as being highly successful.
Qatar previously held 21.4pc of IAG, which also owns Spanish carriers Iberia and Vueling and the UK's British Airways.
The cost of increasing its IAG holding is £465m (€559m), based on the closing price of IAG's shares on Tuesday.
Qatar first invested in IAG in 2015, buying 9.99pc of the company, and has steadily increased it since then.
It also owns stakes in China Southern and Cathay Pacific, and said earlier this month it was in talks about doubling its holding in LATAM Airlines to 20pc and buying a 49pc stake in Africa's RwandAir.
It said it continued to support IAG and its strategy.