Elon Musk became the world's first trillionaire after shares of his rocket company SpaceX soared in Wall Street's biggest initial public offering of stock.

Shares in SpaceX jumped more than 19 per cent after opening for trading at noon Friday, a sign that investors are looking past the billions the company is losing and instead betting that its massive investments in satellites, orbital data centres and artificial intelligence will pay off in the future.

SpaceX opened at US$150 a share, then rose to about US$168, before finishing the day just above US$161. That price gave the company a market value of US$2.1 trillion, making it the sixth largest public US company, larger even than its founder and CEO's other big business, the electric vehicle maker Tesla.