SpaceX must take a series of steps before it can launch its mega rocket again after its debut ended in an explosion, federal regulators said Friday.

The Federal Aviation Administration said it closed its investigation into SpaceX’s failed debut of Starship, the world’s biggest rocket. The agency is requiring SpaceX to take 63 corrective actions and to apply for a modified FAA license before launching again.

FAA official said multiple problems led to the April launch explosion, which sent pieces of concrete and metal hurtling for thousands of feet (meters) and created a plume of pulverized concrete that spread for miles (kilometers) around.

SpaceX founder Elon Musk said in the accident's aftermath that he improved the 394-foot (120-meter) rocket and strengthened the launch pad. A new Starship is on the redesigned pad, awaiting liftoff. It will fly empty, as before.

During the initial test flight, the rocketship had to be destroyed after it tumbled out of control shortly after liftoff from Boca Chica Beach. The wreckage crashed into the Gulf of Mexico. SpaceX said fuel leaks during ascent caused fires to erupt at the tail of the rocket, severing connection with the main flight computer and leading to a loss of control.

That flight “provided numerous lessons learned,” the company said in a statement.

NASA wants to use Starship to land astronauts back on the moon in another few years. Musk's ultimate goal is to build a fleet of Starships to carry people and supplies to Mars.