A new air leak problem on the International Space Station (ISS) has forced NASA to postpone a mission with human passengers. NASA announced that they are postponing Axiom Mission 4 which included sending four astronauts on a commercial flight to the space station. The organization provides limited information regarding the situation.

Despite outward appearances there remains genuine concern behind the scenes. Several sources have verified to Ars Technica that NASA is actively assessing possible structural problems in a space station that has operated for almost three decades.

The ISS has previously dealt with air leak problems. The Russian Zvezda service module has been identified as the source of a gradual yet ongoing pressure reduction since 2019. The problematic area remains focused on PrK (a transfer tunnel) which serves as the link between the module and the docking port for Soyuz and Progress spacecraft.

Russian cosmonauts performed various temporary repairs aboard the station by sealing cracks and experimenting with different sealants. Temporary repairs effectively reduced the leak rate to about two pounds of air each day. The most effective long-term strategy? The best long-term solution involved maintaining the PrK hatch closed whenever it wasn’t needed.

That approach worked—until recently.

This month Roscosmos shared news that the PrK module had been “completely sealed.” NASA confirmed the statement and reported that the recent repairs were effective because the leak rate inside PrK had ceased.

That sounds like progress. But then a new problem emerged: The total air pressure inside the International Space Station experienced an ongoing decline.

Sources familiar with the situation indicate the probable cause of the problem centers around the hatch seals. Air from the station’s main body escapes through the hatch and enters the PrK module which maintains stable pressure creating a false impression that PrK is no longer leaking while air loss continues throughout the station.

This has left engineers scratching their heads. What remains unclear is the current situation since the module shows no signs of leaking and repairs remain secure.

Although the present air loss does not pose immediate danger, it prompts important concerns regarding the future structural stability of the ISS. High cycle fatigue represents one of the most concerning scenarios because it causes metal materials such as aluminum to deteriorate after extended time periods.

Imagine repeatedly bending a wire to and fro. The first time, it bends. After a few times, it breaks. Metal fatigue represents a condition that can lead to abrupt and unexpected failures.

Since its segments began launching in 1998 the ISS has now reached its third decade while orbiting Earth. The space station has been subjected to extreme thermal cycles and pressure changes along with structural stress for over thirty years.

NASA’s internal risk evaluations place structural cracking at the maximum risk level within their 5×5 risk assessment grid. In simple terms: The agency identifies structural integrity as its primary concern.

It’s not just theory either. In 1988 a tragic metal fatigue incident happened when Aloha Airlines Flight 243 experienced a mid-flight decompression because of concealed fuselage cracks. The plane held together—barely.

NASA has postponed the launch of the Axiom-4 mission originally set for Thursday because of prevailing uncertainties.

NASA and Roscosmos now have extra time to analyze the situation because mission Axiom Mission 4 has been postponed.

The tentative launch date for June 18 stands subject to conditions. Should the leak problem remain unresolved or become more severe the launch date might face another delay.

Engineers together with leadership personnel are persistently evaluating the current situation in the background. A source who knows about internal discussions said NASA personnel are feeling worried.

NASA has not yet conducted a press conference or released a detailed report explaining the leak despite mounting inquiries from journalists and observers. The only public statement to date?

The International Space Station crew is performing standard operations without any safety concerns.

And for now, that’s true. The astronauts are safe, and operations continue. The International Space Station (ISS) ages while visible signs of fatigue increase yet the question remains unanswered:

The solution depends both on the metal’s durability and on the agencies’ capacity to respond promptly and transparently.