June 26 (Reuters) - Even by SpaceX standards, Friday is shaping up as an eventful trading session as investment funds tracking Russell indexes prepare to add billions of dollars' worth of Elon Musk's internet and rocket company to their holdings.

After a blockbuster initial public offering this month, SpaceX's stock has been on a wild ride, soaring 67% to its June 16 intraday high of $225.64 before tumbling to Thursday's $153 close.

The stock remains well above the $135 IPO price as investors assess how to value a company that lost $4.9 billion last year, but that backers expect to dominate the satellite internet, AI and commercial space launch markets that they believe will define the next decade of global infrastructure.

FTSE Russell will add SpaceX to its Russell U.S. indexes after Friday's close of trading as part of its semi-annual index reconstitution. That means passively managed exchange-traded funds that track Russell indexes, such as the iShares Russell 1000 ETF, will have to add SpaceX shares to their portfolios. The event will likely take place in a narrow window toward market close on Friday as fund managers attempt to minimize the "tracking error" between their funds' performance and the index that can result if their buy-in price differs from the closing price.

While SpaceX's $2 trillion market capitalization makes it almost as valuable as Amazon, only about $100 billion of shares have been listed for trading on the stock market, with the rest owned by Musk, other insiders and employees. Passively managed funds will need to buy almost $3 billion worth of SpaceX shares to match the Russell indexes they track, Jefferies estimated in a report this month. That could mean a squeeze as Friday's closing auction approaches, though options positioning appeared muted.

SpaceX options contracts set to expire on Friday are priced for a share price swing of 3.6% in either direction by the end of the week, Trade Alert data showed.

SpaceX is also set to be added to the tech-heavy Nasdaq 100 in July, an event that will force large index funds such as the Invesco QQQ ETF, which tracks that index, to buy its shares.

Following its losses in recent sessions, SpaceX is trading at 107 times its 2025 sales, an astronomical valuation. By comparison, AI heavyweight chipmaker Nvidia recently traded at 21 times sales.

S&P Global blocked SpaceX from joining the S&P 500 index after it said this month it would not change its inclusion criteria to accommodate megacap IPOs. To ​be included in the S&P 500, a company must be profitable in its most recent quarter as ​well as for the sum of its most recent four quarters, according to one of the rules S&P left unchanged.

The S&P 500 addition in 2020 of another Musk company, Tesla, resulted in a closing squeeze that sent shares up 6%.