Speaking at the Paris Air Show in Le Bourget this Tuesday, Bridenstine stopped short of offering a clear flight timeline for its multibillion-dollar Commercial Crew Program, and said he would not prejudge the results of an investigation into the incident.
'Schedule will change'
He told reporters at Le Bourget: "There is no doubt the schedule will change. It won't be what was originally planned."
Bridenstine's comments cast fresh doubt on billionaire Elon Musk's goal of returning astronauts to the orbiting research laboratory from U.S. soil this year, though a person familiar with the matter said SpaceX has privately expressed confidence that it can rebound.
For years, the United States has had to rely on Russia for rides to the space station and the Commercial Crew Program's goal is to change that.
Boeing Co, the other contractor hired by NASA to develop a separate rocket-and-capsule system to fly astronauts to space, has also delayed its own flights for months.
Adding to the doubts, NASA has said it is considering paying for two more seats to the space station for autumn of 2019 and spring of 2020 to ensure U.S. access.
Originally, SpaceX's astronaut flight was planned for July following a successful six-day round-trip unpiloted mission in March.
The April 20 accident occurred at Cape Canaveral Air Force Station as SpaceX was about to test eight emergency thrusters designed to propel the capsule, dubbed Crew Dragon, to safety from atop the rocket in the event of a launch failure.
NASA has awarded $6.8 billion to SpaceX and Boeing to develop their separate capsule systems.
Bridenstine also pledged better communication and transparency after the agency and SpaceX were criticised over a reluctance to describe in plain terms what happened to the capsule for days after the incident.
That stance was at odds with NASA's long history of transparency surrounding accidents involving its human spaceflight program.