SpaceX’s latest Starship prototype rocket managed to reach an altitude of more than 8 miles on Wednesday. Unfortunately, landing the spacecraft proved more difficult as the company failed to stick a safe landing.

The spacecraft exploded following its six-and-a-half-minute test flight. Despite the failure, SpaceX’s chief executive officer, Elon Musk, called the test a “success.” The latest test flight of the prototype, called the SN8, is one of the most complicated ever done by the company to date.

According to SpaceX, the purpose of the suborbital flight was to test how the vehicle’s engine would function during an actual flight, among other systems. Before the failed landing, the rocket was able to hit its targeted altitude of 8 miles, the highest ever reached by the particular spacecraft design.

SpaceX said that all three of the spacecraft had failed after reaching the altitude and the team attempted to perform a “belly flop” maneuver prior to the crash. Musk said that the problem was traced to the vehicle’s fuel header tank pressure, which was “low during descent.” This caused the vehicle to touchdown at a higher velocity than initially planned.