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

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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 percent stake in Hilton for around $6.5 billion to become its biggest shareholder.

Today, HNA owns 26.1 percent of Hilton.

Following a $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 last year, HNA’s bank loans and bonds surged by more than one-third to 637.5 billion yuan ($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 $3.5 billion from $3 billion. The lenders are JPMorgan Chase & Co JPM.N, Credit Suisse AG CSGN.S, Deutsche Bank AG DBKGn.DE and UBS AG UBSG.S.

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 percent at $78.79 in late morning trade.

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

(The story corrects to “first 11 months of last year” from “this year” in fifth paragraph.)