Billionaire Gautam Adani's airport company is set to rank among the world's most valuable airport operators after securing about $1 billion in fresh equity from global and domestic investors, including Temasek, BlackRock-managed funds, Alpha Wave Global, and Premji Invest.

The transaction values Adani Airports Holdings at about $18 billion before the investment.

With the new capital, the implied post-money equity value is about $19 billion, putting the Indian airport operator around third globally among major listed and recently valued airport operators by equity value, behind Spain's Aena and Airports of Thailand, according to market research analysts.

The comparison, however, may not strictly be like-for-like because Aena and Airports of Thailand are publicly traded companies, while Adani Airport Holdings is privately held within Adani Enterprises.

Under the agreements, the investor consortium will acquire newly issued shares in Adani Airport Holdings in three tranches and will collectively hold about 5.54 per cent once the transaction is completed.