“Preliminary analysis show[s] the increased drag at the low altitudes prevented the satellites from leaving safe-mode to begin orbit raising maneuvers, and up to 40 of the satellites will reenter or already have reentered the Earth’s atmosphere,” SpaceX said in a statement Tuesday.

The space tech company, which Musk founded 20 years ago, conducted the launch on Feb. 3, deploying 49 Starlink satellites into low earth orbit from a Falcon 9 rocket. But the next day, a geomagnetic storm—which occurs when charged particles kicked out from the Sun in a solar flare interact with the Earth’s atmosphere—forced engineers to abort the mission.

“These storms cause the atmosphere to warm and atmospheric density at our low deployment altitudes to increase,” SpaceX said, explaining that the higher atmospheric density increased drag on the orbiting Starlink satellites, preventing them from moving to higher altitudes. Reuters reports the 40 lost modules mark the largest number of satellites knocked out by a single geomagnetic event ever.

According to SpaceX, the company always deploys Starlink satellites at a low orbit first, before directing the modules to increase altitude. The two-stage deployment reduces the risk of dysfunctional satellites becoming space junk, which drifts around space. The approach makes it easier to identify faulty satellites and return them to Earth—so to speak.

SpaceX says Starlink satellites are designed to break up and burn upon reentry to Earth’s lower atmosphere, so they never actually return to Earth. On Tuesday the company said “the deorbiting satellites pose zero collision risk with other satellites…and no satellite parts [will] hit the ground.”

SpaceX doesn’t disclose the cost of its Starlink satellites, but some analysts have put the cost of each module between $250,000 and $500,000, meaning a fleet of 40 would cost $20 million at most. Meanwhile, SpaceX disclosed in 2020 that each Falcon 9 launch costs around $30 million, so in total, this abortive operation could have cost SpaceX around $50 million in sunk costs.

SpaceX has already deployed 1,469 Starlink satellites into orbit and is targeting a grand total of 30,000. Together, they will form the infrastructure to back Musk’s plan of delivering high-speed internet to remote regions across the globe.

SpaceX says its Starlink network is already serving 145,000 users across 25 countries, and the company is reportedly in talks to reconnect the island nation of Tonga to the internet, after a massive volcanic eruption last month severed the undersea cables connecting the Pacific islands to the World Wide Web.

If successful, the Starlink network could revolutionize access to the internet, upending current systems of control that governments use to censor or block internet access. Although the Starlink network would be under SpaceX’s control instead and comes at a cost: roughly $99 per month for the end user.

The company has already received blowback from astronomers and governments that are concerned about the growing flotilla of satellites Musk is positioning in space. This week, NASA delivered a letter to the Federal Communications Commission (FCC) warning that Musk’s plan for 30,000 low-orbit satellites will increase the risk of Starlink modules colliding with other space vehicles.

SpaceX previously said there is “zero risk” of a Starlink module colliding with a large spacecraft because of the former’s maneuverability. But last December, China complained to the UN that its new space station had to take evasive action twice to avoid a collision with Starlink satellites last year.

And, as demonstrated by 40 out of 49 Starlink satellites falling from the sky, SpaceX doesn’t always have as much control over its modules as it would like.