Narrative:

On takeoff roll left pack high stage light came on. The takeoff was continued as the runway was wet and we were high speed although below V1. After, the left pack and bleed were secured. 3 hours into flight at FL350 the cabin altitude warning sounded. Cabin altitude was 10300 ft. We asked for an immediate descent and were told unable due to traffic. We declared an emergency and began a descent to FL210. As we descended the left pack and bleed were opened and used to assist in regaining control of cabin. This and the descent brought the cabin down to 6400 ft. FL210 was not acceptable due to thunderstorms and moderate turbulence and with control of the cabin we climbed to a smoother FL280 where we finished the flight. Emergency was canceled prior to climbing back to altitude.

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Original NASA ASRS Text

Title: A B757-200 IN CRUISE AT FL350 DECLARED AN EMER AND MADE EMER DSCNT TO FL210 WHERE CABIN PRESSURE WAS REGAINED. CAUSE UNKNOWN.

Narrative: ON TKOF ROLL L PACK HIGH STAGE LIGHT CAME ON. THE TKOF WAS CONTINUED AS THE RWY WAS WET AND WE WERE HIGH SPD ALTHOUGH BELOW V1. AFTER, THE L PACK AND BLEED WERE SECURED. 3 HRS INTO FLT AT FL350 THE CABIN ALT WARNING SOUNDED. CABIN ALT WAS 10300 FT. WE ASKED FOR AN IMMEDIATE DSCNT AND WERE TOLD UNABLE DUE TO TFC. WE DECLARED AN EMER AND BEGAN A DSCNT TO FL210. AS WE DSNDED THE L PACK AND BLEED WERE OPENED AND USED TO ASSIST IN REGAINING CTL OF CABIN. THIS AND THE DSCNT BROUGHT THE CABIN DOWN TO 6400 FT. FL210 WAS NOT ACCEPTABLE DUE TO TSTMS AND MODERATE TURB AND WITH CTL OF THE CABIN WE CLBED TO A SMOOTHER FL280 WHERE WE FINISHED THE FLT. EMER WAS CANCELED PRIOR TO CLBING BACK TO ALT.

Data retrieved from NASA's ASRS site as of July 2007 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.