Boeing postponed the test launch of its uncrewed Starliner astronaut capsule on Tuesday, the company said in a statement. The delay was caused by a technical issue that popped up after lightning storms on Monday. Mission teams are determining whether the issues can be resolved in time for Starliner’s next launch opportunity on Wednesday around noon.

During routine engineering checks the day before Starliner’s planned launch, engineers noticed the position of some valves within Starliner’s propulsion system appeared out of place, Boeing said, adding that the issue was detected “following yesterday’s electrical storms in the region of Kennedy Space Center.” Starliner was slated to launch atop a United Launch Alliance Atlas V rocket on Tuesday at 1:20PM ET. But now “Boeing and NASA teams are assessing the situation” to see whether Starliner can fly on Wednesday at 12:57PM ET.

The Starliner launch is a test mission without any humans aboard. It’s poised to fly to the International Space Station, demonstrate a clean docking procedure, and stay docked for roughly ten days before returning back to Earth. The mission comes more than a year and a half after Boeing’s first orbital Starliner test failed to reach the station and returned home earlier than planned in 2019.

Tuesday’s launch “scrub” — industry jargon for a launch delay — marks Starliner’s second so far. The spacecraft was initially set to fly to space on Friday, July 30th, but a mishap involving Russia’s new science module at the ISS forced Boeing to postpone the launch to Tuesday as NASA made sure the space station was safe and ready for a new spacecraft arrival.