Shares of Virgin Galactic fell in trading on Thursday after the company announced plans to raise up to $500 million in debt.

“The company intends to use the net proceeds from the offering to fund working capital, general and administrative matters and capital expenditures to accelerate the development of its spacecraft fleet,” Virgin Galactic said in a press release.

The company intends to raise $425 million from the sale of 2027 convertible senior notes through a private offering, with an additional $75 million option also expected to be granted to buyers.

Virgin Galactic stock fell as much as 12% in premarket trading from its previous close of $12.37.

Sir Richard Branson’s Virgin Galactic went public via a merger with a special purpose acquisition company, or SPAC, from Chamath Palihapitiya in October 2019. While the space tourism company said during its debut that it planned to begin flying customers in 2020, delays to its spacecraft testing and development have steadily pushed that schedule back.

After launching Branson and three other company employees on a test spaceflight in July 2021, further delays have pushed Virgin Galactic’s beginning of commercial service to late this year at the earliest.