SpaceX successfully launched a new batch of its Starlink satellites on Monday morning, but the first stage of the Falcon 9 rocket that put them in orbit missed its landing on a floating platform at sea. It’s the first time that’s happened in almost four years; the last time Falcon 9 booster failed to land on one of SpaceX’s drone ships was in June 2016.

To be sure, SpaceX has lost a few rocket boosters since then. The company has lost the center core of the three-core Falcon Heavy two out of three times in that rocket’s first few launches. A Falcon 9 booster also missed the landing pad at Cape Canaveral in December 2018, spiraling into the sea instead after a failure with one of the gridded fins that stabilize its descent. SpaceX has also not attempted landings on about a dozen missions since that 2016 miss — something it usually does when the missions require the rocket to reach higher velocities that make landings more difficult.

The booster supporting this mission previously launched the CRS-17 mission in May 2019, the CRS-18 mission in July 2019, and the JCSAT-18/Kacific1 mission in December 2019 pic.twitter.com/WWLc1LPxJj — SpaceX (@SpaceX) February 14, 2020

SpaceX’s run of successful landings has been a boon for its business. The more rocket stages it recovers, the more it can reuse for future flights. (This booster, for instance, made its fourth flight on Monday.) Reusing rockets is a way to lower the massive cost of getting to space. Not only has SpaceX gotten really good at catching and reusing its rocket stages, but it’s also doing it faster than ever. The rocket launched Monday was last used just 72 days ago, meaning the private spaceflight company almost broke the record for fastest turnaround held by NASA’s space shuttle.

It’s not yet clear what happened during Monday’s attempted landing. On the broadcast, all that could be seen was a puff of smoke or steam to the side of the drone ship, indicating that the Falcon 9 booster missed the platform by a fairly wide margin. “We clearly did not make the landing this time,” Lauren Lyons, one of SpaceX’s engineers, said on the broadcast. What is clear, though, is that SpaceX has fully flipped the perception of its sea landings. The company struggled with the first few attempts back in 2015, losing a number of rocket boosters at sea. Now, they’ve become another part of the company’s regular routine.