Air leakage on the International Space Station (ISS) has intensified to the point where it postpones an upcoming crewed mission. NASA has announced a delay for Axiom Mission 4 which was carrying four astronauts to the space station. NASA has not disclosed much additional information about the situation.

The concern exists behind the scenes. According to several sources who spoke with Ars Technica NASA is responding with urgency to the possible structural flaws of the space station that has orbited Earth for almost three decades.

The International Space Station has previously experienced issues with air leaks. The Russian Zvezda service module has been identified as the source behind the gradual pressure loss reported since 2019. The primary area of concern is the PrK section which serves as a transfer tunnel connecting the Zvezda service module to the docking port that Soyuz and Progress spacecraft use.

Russian cosmonauts executed multiple temporary repairs that included sealing cracks and evaluating new sealing materials. The temporary repairs succeeded in reducing the air leak to a manageable rate of roughly two pounds per day. The most effective long-term strategy? The most successful solution for reducing the leak was to keep the PrK hatch shut when it wasn’t needed.

That approach worked—until recently.

Roscosmos confirmed this month that the PrK module has been fully sealed. NASA confirmed the statement about successful repairs which stopped the air leak within the PrK module.

That sounds like progress. But then a new problem emerged: Air pressure inside the ISS exhibited a steady decline.

The two informed sources suggest that the hatch seals are the probable cause of the problem. The hypothesis suggests that air from the station’s main compartment escapes through the hatch into the PrK module which maintains stable pressure thus creating a deceptive appearance that the PrK module has stopped leaking air while the station continues to experience overall air pressure loss.

This has left engineers scratching their heads. The module shows no signs of leakage and repairs appear to be successful, yet there remains an unresolved issue.

The current air loss poses no immediate danger but prompts serious concerns about the future structural soundness of the ISS. High cycle fatigue represents one of the most concerning scenarios which leads to gradual damage in metals like aluminum during extended time periods.

Visualize repeatedly bending wire in opposite directions. The first time, it bends. After a few times, it breaks. Metal fatigue occurs when materials fail suddenly and unexpectedly.

The ISS began its journey in space with segmented launches starting in 1998 and has been operating in orbit for nearly thirty years. The structure has endured extreme thermal cycles together with pressure changes and structural stress for thirty years.

NASA’s risk assessments place structural cracking at the top position within their 5×5 risk evaluation matrix. In simple terms: Structural cracking represents one of the greatest concerns for the agency according to their risk assessments.

It’s not just theory either. An incident of metal fatigue led to a catastrophic decompression event in 1988 when Aloha Airlines Flight 243 experienced mid-flight structural failure because of undetected fuselage cracks. The plane held together—barely.

NASA postponed the Axiom-4 mission launch originally scheduled for Thursday because of uncertainties.

The statement from the agency confirmed that postponing Axiom Mission 4 allows NASA and Roscosmos extra time to review the current circumstances and decide if further troubleshooting actions are required.

NASA has set a provisional launch date for June 18 although it remains subject to change. The launch date may face another delay if the leak situation remains unresolved or deteriorates further.

Engineers alongside leadership are continuously evaluating the situation behind the scenes. An insider who spoke about internal discussions reported that the NASA team feels “worried.”

NASA has not yet organized a press conference or delivered a full explanation about the leak situation even though journalists and observers continue to ask more questions. The only public statement to date?

The International Space Station’s crew continues to perform standard operations while maintaining safety.

And for now, that’s true. The astronauts are safe, and operations continue. The International Space Station continues to age which leads to more noticeable signs of fatigue while raising important questions.

The station’s ability to operate safely may depend on both the metal’s strength and the response speed and clarity of the involved agencies.