By Ben Otto

Singapore Airlines has raised an additional 750 million Singapore dollars (US$541.3 million) in long-term loans, as it seeks to bolster liquidity in the face of the Covid-19 pandemic.

The Singapore carrier said Thursday that it had secured the new financing on some of its Airbus A350-900 and Boeing 787-10 jets. The airline has now raised a total of S$1.65 billion from secured financing since the start of the current fiscal year, it said.

Like many carriers around the world, Singapore Airlines has been hit hard by the pandemic and resulting travel restrictions. It has grounded many of its jets due to low demand and warned of severe financial and operating challenges to its business.

For the current fiscal year, the company has raised about S$11 billion to withstand the crisis, with the lion's share coming from a rights issue.

The airline added Thursday that all existing committed lines of credit that were to come due in 2020 have been renewed to 2021 or later, giving the company more than S$2.1 billion in committed liquidity.

"During this period of high uncertainty, SIA will continue to explore additional means to shore up liquidity as necessary," it said. It added that it retains the option to raise up to S$6.2 billion in additional mandatory convertible bonds if needed.

Write to Ben Otto at ben.otto@wsj.com