A technical malfunction has postponed the historic flight of an international crew to the International Space Station.

The latest delay in the launch of the Ax-4 mission to the International Space Station (ISS) is caused by a technical problem discovered in the Falcon 9 rocket of SpaceX. A liquid oxygen (LOx) leak in the first stage of the rocket was detected during the post-test inspections after the static engine test conducted on June 8.

According to Bill Gerstenmaier, Vice President of Flight Reliability at SpaceX, the same leak was observed during a previous flight of the same first stage, upon its re-entry into the Earth's atmosphere. The company either did not fully identify the problem during maintenance or did not adequately resolve it. SpaceX is now installing a new venting system that should eliminate or minimize the leak.

The spacecraft bound for the ISS will carry four astronauts: Peggy Whitson (mission commander, former NASA astronaut, now Director of Astronaut Programs at Axiom Space), Shubhangshu Shukla (India, pilot), Sławosz Uznański-Wiśniewski (Poland, European Space Agency, mission specialist) and Tibor Káposzta (Hungary, mission specialist). For the three astronauts from India, Poland, and Hungary, this will be their first flight to the ISS.

The Ax-4 crew will remain on the station for about two weeks, performing around 60 scientific experiments. The return to Earth is planned with a splashdown in the Pacific Ocean. This is the fourth mission of Axiom Space to the ISS.

The launch delay is not related to the spacecraft itself, but to technical issues with the launch vehicle. SpaceX is actively working to resolve the defect and will announce a new date as soon as it is determined.