(Adds Air France detail in paragraphs 4-5, analyst comment in paragraphs 8-10, updates shares in paragraph 7)

COPENHAGEN, Oct 4 (Reuters) - SAS shares slumped by as much as 95% on Wednesday after the airline announced a financial restructuring on Tuesday to prevent bankruptcy, bringing on board big new investors and wiping out the stakes of its more than 250,000 owners.

Scandinavia's biggest carrier filed for bankruptcy protection in the United States in mid-2022 after years of struggling with high costs coupled with low customer demand exacerbated by the coronavirus pandemic.

SAS said U.S. investment firm Castlelake and Air France-KLM would become new major shareholders alongside the Danish state, and that the airline's stock will be delisted from the Stockholm, Copenhagen and Oslo exchanges.

Air France-KLM, for whom the deal is the first since the group consolidated nearly 20 years ago, said it would aim to tie SAS flights into those of its own airlines in its Amsterdam and Paris hubs to strengthen its Nordic presence.

"Air France-KLM is determined to play an active role in the consolidation of European aviation," it said.

Castlelake will take a stake of about 32%, Air France-KLM will own around 20%, Danish investor Lind Invest 8.6% and the Danish state about 26%, SAS said, adding that the remaining equity will likely be distributed among creditors.

Shares in SAS, which have tumbled in recent years, traded down 83% at 1144 GMT to 0.05 Swedish crowns ($0.0045).

Sydbank analyst Jacob Pedersen said the fact that the shares still traded at any residual value could be explained by the potential for legal challenges or investor "overconfidence."

"Management itself has come out to say there was a risk that the shares will become worthless. Now we know the shares will become worthless," Pedersen said.

"If you can't find someone even more opportunistic and risk averse than yourself to sell it to, you will ultimately end up with a loss," he added. ($1 = 11.0295 Swedish crowns) (Reporting by Louise Breusch Rasmussen in Copenhagen, Anna Ringstrom in Stockholm, editing by Terje Solsvik and Alexander Smith)