NASA astronauts Bob Behnken and Doug Hurley may spend more time on the International Space Station than originally planned when they ride SpaceX’s new human-rated Dragon spacecraft into orbit on its first crewed test flight, a space agency official said Friday.

SpaceX test-fired a Falcon 9 rocket Friday at Cape Canaveral in preparation for liftoff as soon as Sunday with the company’s fifth batch of Starlink broadband satellites.

A critical test-firing of the Space Launch System’s core stage engines cut off about a minute into a planned eight-minute burn Saturday on a test stand at NASA’s Stennis Space Center in Mississippi. The rocket’s four engines ignited at 5:27 p.m. EST (2227 GMT) for a test that was to pave the way for the core stage’s shipment to the Kennedy Space Center for launch preparations.