SpaceX is preparing to sell insider shares in a transaction that would value Elon Musk’s rocket and satellite maker at as much as $800 billion, people familiar with the matter said, reclaiming the title of the world’s most valuable private company.

Elon Musk’s SpaceX has told investors and financial institution representatives that it is aiming for an initial public offering in the second half of next year, according to two people familiar with the discussions.