In May 2017, Singapore Airlines had already poured over S$100 million into Vistara, doubling its initial investment plan. By April 2019, Tata and SIA had injected a combined 40.2 billion rupees into the carrier, boosting its paid-up capital to 56.4 billion rupees.

During the COVID-19 pandemic, from April 2020 to August 2021, the two shareholders provided 18.3 billion rupees to keep Vistara afloat, with additional rounds in May and August 2021 totaling 5.95 billion rupees from SIA. By 2023, SIA's total investment in Vistara had reached approximately S$900 million.

In January 2022, Tata Sons acquired full ownership of Air India from the Indian government, without SIA's participation. Later that year, in October, SIA confirmed confidential discussions with Tata about a potential merger, and by November, the two parties had signed a formal agreement to merge Vistara into Air India.

Under the deal, SIA exchanged its 49% stake in Vistara and invested 20.585 billion rupees (about US$250 million) for a 25.1% share of the enlarged Air India, with a commitment to provide up to an additional 50.2 billion rupees if needed. The merger was completed on November 12, 2024, making Air India an associated company of SIA.

Following the merger, SIA made another capital injection of 10.807 billion rupees in March 2025, bringing its total investment in Air India to S$2.096 billion. In April and May 2025, India and Pakistan engaged in armed conflict, leading Pakistan to close its airspace to Indian carriers, forcing them to reroute flights.

On June 12, 2025, an Air India flight to London crashed shortly after takeoff from Ahmedabad, prompting the airline to implement a safety pause and conduct additional checks on its Boeing 787 fleet.