Atlantis aging issue.

"NASA announced that 24 helium and nitrogen gas tanks, named Composite Overwrap Pressure Vessels, in the Space Shuttle Atlantis are older than their designed lifetime (designed for 10 years, later cleared for another 10 years but in service now for 22 years). NASA said it cannot guarantee any longer that the vessels on Space Shuttle Atlantis will not burst or explode under full pressure."

[link to en.wikipedia.org]