China's HNA Group Co Ltd, the heavily indebted aviation-to-financials conglomerate, plans to sell some or all of its US$6.3 billion stake in Hilton Worldwide Holdings Inc (HLT.N), underlining its need to shed assets and tackle a cash crunch.

The sale, announced on Thursday through a regulatory filing with the U.S. Securities and Exchange Commission, comes about a year and a half after HNA bought a 25 per cent stake in Hilton for around US$6.5 billion to become its biggest shareholder.

Today, HNA owns 26.1 per cent of Hilton.

Following a US$50 billion investment spree in the past two years, HNA has sold assets such as land and office buildings in recent months to pay down a large pile of debt that is straining its finances.

In just the first 11 months of this year, HNA's bank loans and bonds surged by more than one-third to 637.5 billion yuan (US$101.1 billion), a HNA China bond market filing showed.

HNA had taken out a loan for its Hilton shares as well. A December 2017 SEC filing showed HNA had increased a loan against its Hilton shares to US$3.5 billion from US$3 billion. The lenders are JPMorgan Chase & Co (JPM.N), Credit Suisse AG, Deutsche Bank AG and UBS AG.

No details were available on when or to whom HNA would sell its Hilton stake, or the size of the divestment. A Hilton spokesman declined to comment.

An October 2016 SEC filing showed there are restrictions on how HNA can sell its Hilton stake if a divestiture happens in the first two years of ownership. Limitations included obtaining the approval of a majority of Hilton's board.

Hilton's shares were up 1 per cent at US$78.79 in late morning trade.

HNA sold its 25 per cent stakes in Park Hotels & Resorts (PK.N) and Hilton Grand Vacations Inc (HGV.N) in March. Both stakes were worth a total of US$2.5 billion and were sold in the open market.