Narrative:

During cruise (FL350) astute first officer noticed cockpit O2 gauge was near zero. Considered options (terrain; weather; fuel; etc). Notified maintenance and dispatch. Initiated precautionary descent to 10;000 ft [and] continued normal flight to ord. Cause is under investigation by maintenance when we left aircraft.

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Original NASA ASRS Text

Title: A B737-900 Captain reported his First Officer noticed the crew oxygen system pressure was near zero. They descended to 10;000 FT and continued to destination.

Narrative: During cruise (FL350) astute First Officer noticed cockpit O2 gauge was near zero. Considered options (terrain; weather; fuel; etc). Notified Maintenance and Dispatch. Initiated precautionary descent to 10;000 FT [and] continued normal flight to ORD. Cause is under investigation by maintenance when we left aircraft.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.