Launch of a SpaceX Crew Dragon capsule carrying four astronauts to the International Space Station has been delayed 24 hours to Friday because of bad weather in the Atlantic Ocean where the crew could be forced to ditch in an emergency, NASA announced Wednesday.

Stratolaunch’s rocket carrier jet, the largest aircraft in the world by wing span, took off Saturday morning from the Mojave Air and Space Port in California for its first test flight.

After missing out on an opportunity to win up to $12 million in prize money through DARPA’s Launch Challenge earlier this month, Astra is gearing up for another possible orbital launch attempt next week from Alaska, the company’s chief executive said Friday.