The International Space Station (ISS) has suffered another air leak which is now delaying future crewed missions. NASA announced the delay of Axiom Mission 4 which was set to deliver four astronauts to the orbiting laboratory. The space agency is not providing much information on the situation.

The actual level of concern behind the scenes regarding the situation remains genuine. Both official and unofficial sources have told Ars Technica that NASA is deeply engaged in an investigation of structural issues in the International Space Station which has been orbiting Earth for almost three decades.

The ISS has previously experienced air leakage problems. A persistent pressure decline since 2019 has been identified as originating from the Russian Zvezda service module. The structural issue centers on the PrK section which serves as a transfer tunnel connecting the module to the docking port for Soyuz and Progress spacecraft.

Russian cosmonauts have performed multiple temporary repairs by fixing cracks and experimenting with sealants over the years. The repairs reduced the leak to a manageable rate that remained steady at approximately two pounds of air loss per day. The most effective long-term strategy? The best long-term solution involved keeping the PrK hatch shut whenever it was not needed.

That approach worked—until recently.

Roscosmos confirmed earlier this month that the PrK module had reached the stage of being “completely sealed.” NASA confirmed the statement by reporting that the recent repairs had been successful because they stopped the leak rate within the PrK module.

That sounds like progress. But then a new problem emerged: The International Space Station experienced a continuous decrease in its total air pressure.

Sources familiar with the ISS situation indicate that the hatch seals are the probable cause of the problem. Air from the entire spacecraft is escaping through the hatch to the PrK where pressure measurements show no change resulting in an apparent false sense of leak resolution within the module but ongoing air loss for the station.

This has left engineers scratching their heads. The module shows no signs of leakage and the repairs remain intact so what could possibly be going on?

Although the air loss situation remains non-threatening at present it exposes serious concerns regarding the ISS’s long-term structural integrity. High cycle fatigue represents a major problem because it causes metal materials such as aluminum to deteriorate over extended periods.

Visualize repeatedly bending a wire until it eventually snaps. The first time, it bends. After a few times, it breaks. The phenomenon of metal fatigue presents a dangerous threat because it can occur abruptly and without any prior notice.

Since its launch began in 1998 the ISS has reached nearly 30 years of operation in space. The spacecraft has now undergone thirty years of constant exposure to severe thermal fluctuations together with pressure variations and structural stress.

NASA’s internal risk evaluations place structural cracking at the top position within their 5 by 5 risk matrix. In simple terms: The structural integrity issue stands as one of the agency’s primary concerns.

It’s not just theory either. The 1988 Aloha Airlines Flight 243 tragedy demonstrated metal fatigue when hidden fuselage cracks caused sudden decompression during flight. The plane held together—barely.

NASA delayed the Axiom-4 mission launch due to existing uncertainties.

The agency explained that the Axiom Mission 4 delay gives NASA and Roscosmos more time to assess the situation and decide if further troubleshooting actions are required.

The launch date of June 18 represents a temporary schedule while conditions continue to be assessed. The launch date might face another delay if the leak remains unsolved or shows further deterioration.

Engineers and leadership teams remain actively engaged in evaluating the situation behind closed doors. An insider who knows the internal discussions reported that NASA personnel are expressing concern.

NASA remains silent about the leak incident while journalists and observers increase their questions because the organization has not organized a press conference or shared a comprehensive explanation. The only public statement to date?

Normal operations on the International Space Station continue safely while the crew performs their tasks.

And for now, that’s true. The astronauts are safe, and operations continue. The aging International Space Station shows more fatigue symptoms which makes it hard to ignore the unresolved question.

The safety of the station relies on both metal strength and response speed of the involved agencies.