Air India's owners, Tata Sons, are set to inject more than $1 billion in fresh funding into the lossmaking carrier despite mounting opposition in Singapore. The board approved the capital release at a June meeting, with funds dispensed periodically as Air India meets performance metrics. Tata Sons holds a 75 percent stake in the airline.

Singapore Airlines, which owns the remaining 25 percent, has yet to approve the cash call, stating its board will "carefully consider" any additional requests. Since taking the stake less than two years ago, Singapore Airlines has booked operating losses of about S$1 billion ($780 million) on the ailing carrier. The prospect of further capital calls has proved controversial, with opposition MP Kenneth Tiong criticizing state investor Temasek's role in propping up Air India via Singapore Airlines.

Temasek said it stood by the deal from a long-term perspective. Air India lost $2.8 billion in its most recent financial year and its chief executive Campbell Wilson resigned in April. Tewolde Gebremariam, the former head of Ethiopian Airlines, will take control this month.

N Chandrasekaran, Tata's chair, earlier described Air India's problems as a "perfect storm" and said transformation could take a decade. The airline is also awaiting final findings from an official probe into last year's Ahmedabad crash that killed 260 people. The heavy cost of turning around the airline, along with other capital-intensive bets, was among the key sources of contention between Chandrasekaran and Noel Tata.