Dear SpaceX Stock Fans, Mark Your Calendars for September 21

SpaceX (SPCX), which made a sensational debut on the bourses in June 2026, has been trading relatively sideways since then, although it remains above its initial public offering price (IPO) of $135 per share. This is surprising, considering the company is led by CEO Elon Musk, one of the most volatile and polarizing figures in corporate history whose penchant for making headlines is infamous.

However, on Sept. 21, SPCX stock could get a much-needed boost. Let's take a closer look.

On Sept. 21, a purported increase in SpaceX's publicly traded shares has the potential to add $15.5 billion in passive inflows to the stock following a rebalancing of the Nasdaq-100, according to Wall Street major JPMorgan. Currently, SPCX stock has a weight of 1.25% in the index. With the rebalancing, that is expected to potentially increase to 2.25%.

Valued at a market capitalization of about $1.97 trillion, SPCX stock is down roughly 12% from its opening price of $171.74 on June 15.

However, investors should be cautious before making a beeline for SPCX stock on this news, as additional shares will be available for sale by pre-IPO investors such as insiders, early backers, and employees. By the end of October, more than 1 billion shares are expected to become available, while another tranche of 1.3 billion shares could hit the market after the company posts its third-quarter results in November. Here, though, we must note that while these shares will be tradable, the holders may opt not to sell them, as was evident in an earlier lock-up expiration period in August.

Overall, Nasdaq's actions around SpaceX have been indirectly beneficial for the company. Just shortly before IPO, for example, Nasdaq changed its methodology for inclusion in the index. On May 1, Nasdaq implemented several changes to the Nasdaq-100 methodology. The most important change for SpaceX was a new "Fast Entry" provision. Under the new provision, a newly listed company can enter the Nasdaq-100 on an expedited basis if its full market cap would rank among the top 40 constituents of the Nasdaq-100. "These companies are evaluated on their seventh trading day and, if eligible, added shortly thereafter, with all existing liquidity requirements still applying," Nasdaq noted.