Blue Origin’s New Glenn rocket exploded in a massive fireball while undergoing a test on a Florida launchpad on Thursday evening, dealing a major setback to the Jeff Bezos-backed firm in its efforts to challenge a dominant SpaceX.  

The firm was preparing the vehicle for its fourth launch, which was slated to deploy a batch of satellites for Amazon.com Inc’s Leo, a rival satellite network to SpaceX’s Starlink. None of the satellites were on the rocket when it exploded, a spokesperson for Amazon said.

“Very rough day, but we’ll rebuild whatever needs rebuilding and get back to flying,” Bezos wrote in a post on X.

The rocket experienced an “anomaly” during the test and ll personnel have been accounted for and are safe, the company said on X.

New Glenn, which is key to Blue Origin’s plans for space exploration, is years behind schedule and has faced longer-than-expected waiting periods between flights. The explosion is the latest blow to its reputation as a reliable alternative to SpaceX’s Falcon 9.

It also has a knock-on effect with Amazon’s ambitions to build out its Leo satellite network, which carriers like Delta Air Lines have chosen over SpaceX’s Starlink for inflight Wi-Fi.

The Blue Origin rocket is set to serve a key role in NASA’s Artemis program, which aims to send humans back to the moon. Earlier this week, NASA awarded Blue Origin a lucrative contract to land rovers on the moon.

NASA Administrator Jared Isaacman said the space agency will work with its partners to support a “thorough investigation” of the incident. NASA will provide any information on the impacts to the Artemis and lunar programs as it becomes available.

“Spaceflight is unforgiving, and developing new heavy-lift launch capability is extraordinarily difficult,” Isaacman said in a post on X.

The Federal Aviation Administration, which licenses commercial rocket launches, said it is aware of the failure and there was no impact to air traffic. The test was not within the scope of FAA-licensed activities, the agency said, referring further questions to the company.

The explosion comes almost a year after SpaceX’s Starship rocket burst into flames on a test stand while undergoing a routine static fire test in Texas. Starship is intended to serve as the primary spacecraft for ferrying humans and cargo to Mars.

Last week, Starship successfully reached space and deployed 20 mock satellites but its booster failed to perform an expected engine burn and spun out of control as it came back down over the Gulf of Mexico. As a result, the US Federal Aviation Administration has temporarily grounded the spacecraft.

As the space race in the US heats up, SpaceX is currently preparing to go public, targeting a valuation of at least $1.8 trillion, Bloomberg News has reported. This would make it the biggest IPO of all time.

The New Glenn rocket is one of an elite group of vehicles that is supposed to deliver the most critical US national security satellites to orbit for the Pentagon.

Blue Origin recently launched New Glenn on its third flight in April. The rocket successfully took off and the vehicle’s booster landed on a company barge at sea.

However, the upper portion of the rocket experienced an issue in space and didn’t achieve enough thrust, failing to put the satellite it was carrying for AST SpaceMobile Inc into the proper orbit. Ultimately, the satellite fell back to Earth and burned up in the atmosphere.

The FAA had recently approved Blue Origin’s investigative report that analyzed the issue on the third flight, and the company said corrective measures had been implemented.