Sir Richard has gradually reduced his stake in Virgin Galactic during the pandemic, despite its rising share price and the company successfully transporting the 71-year-old to the edge of space last month.
Virgin has used the share sales, which total US$950m, will be used to support sister companies such as Virgin Atlantic and cruise line Virgin Voyages, which have been hit hard by the pandemic.
If Sir Richard's Galactic stake were to fall below 25 per cent he would lose a second board appointment as well as a veto over sales, acquisitions and dividends. Its existing three appointees are former Virgin Atlantic boss Craig Kreeger, Virgin investment chief Evan Lovell and former Goldman Sachs executive George Mattson.
Sir Richard fulfilled a decades-long ambition to travel to the edge of space last month, a step towards Virgin Galactic transporting members of the public. It recently resumed selling tickets for US$450,000, double the price at which it had previously sold reservations.
Shares in the US$6.5 billion company have swung wildly since it went public in 2019, as it has joined the ranks of so-called "meme stocks" pumped up by online traders.
A spokesperson said Sir Richard continued to be Virgin Galactic's largest shareholder.