U.S. regulators on Friday cleared SpaceX to restart launching its stalwart Falcon 9 rocket, as a probe continues into a rare mishap earlier this week during a first-stage booster landing.

The Federal Aviation Administration (FAA) grounded the Falcon 9 on Wednesday after the first-stage booster tipped over and exploded while attempting to land on a droneship off the Florida coast.

The early morning launch was otherwise successful, delivering the latest batch of 21 Starlink internet satellites into orbit.

"The SpaceX Falcon 9 vehicle may return to flight operations while the overall investigation of the anomaly during the Starlink Group 8-6 mission remains open, provided all other license requirements are met," the FAA said in a statement on Friday.

A webcast from Elon Musk's company showed the first stage, which normally fires its thrusters to achieve a precise upright landing, tilting and blowing up as it descended onto a droneship off the Florida coast.

Although landing the booster is a secondary objective, and no lives or public property were at risk, the reusability of the entire rocket system is crucial to SpaceX's business model.

This incident broke a more than three-year streak of hundreds of successful booster landings.

The Falcon 9 is the workhorse of SpaceX's fleet, trusted by the U.S. government and private industry to propel satellites and astronauts into orbit.

It was last grounded for around two weeks in July when its second stage engine experienced an anomaly that prevented it from deploying another batch of Starlink satellites at the correct altitude, causing them to burn up upon re-entry through Earth's atmosphere.

Upcoming SpaceX launches

The company is due to launch two critical missions. The first, the Polaris Dawn mission, will take a crew of private citizens on a pioneering commercial spacewalk, marking a first in the industry. This launch, initially scheduled for an earlier date, has faced postponements due to ground system complications and unfavorable weather conditions.

In late September, SpaceX is also targeting the launch of Crew-9, which will send two NASA astronauts to the International Space Station. This mission is part of a broader plan to return the Boeing Starliner's test flight crew to Earth in 2025 after their extended stay in space.

(With input from AFP)