Narrative:

We briefed with the crew that brought our airplane on weather and turbulence. They advised us that the flight previous to theirs a 'bleed trip off' had been encountered and logged in the forms but that they had no issues with that system. I reviewed that write-up during ground ops. We had a routine takeoff. Approximately 25 minutes into the flight we observed a bleed trip off indication. We applied the QRH procedure which lead to shutting down the left pack. At this point we still had ACARS capability so I contacted the dispatcher and asked him to get maintenance on the line with us. I briefed them on the bleed trip event and then queried further whether they knew of any altitude restrictions with a pack shut down. The bleed trip procedure had no altitude restrictions included. With no restrictions noted we continued to our assigned altitude of FL380 which was the smoothest ride. For about an hour the flight went well with no issues and the cabin altitude remained steady. Approximately [hour and a half] into the flight we got a cabin altitude warning along with the warning horn. We saw the cabin altitude at about 11;000' as we executed the immediate action items. We began the turn away and descent procedure from the diversion guide and once established completed the emergency descent checklist. As we continued with the descent we noted that the cabin altitude remained near the 11;000' mark and as we descended through the high 20's the cabin started slowly coming down. We were able to contact arinc and alert them of our location and descent procedure. They soon patched us in with dispatch and we advised him of our situation. As we got below the track system we began a turn towards the east coast of florida and began looking for an appropriate airport to recover to. I advised the flight attendants of our situation and gave a test briefing. The cabin masks did not drop as we never got above 11;000' cabin altitude. As we descend through approximately 20;000' the cabin altitude was below 10;000' and slowly coming down. We decided to level at 14;500' where we observed the cabin to be steady at 6;000'. Discussions with dispatch lead to an agreement that [an alternate] was the best recovery option given weather; distance; and passenger accommodations. As the aircraft condition was now stable we coordinated the recovery and requested no emergency vehicles. Throughout the very busy scenario; communication between myself and first officer; arinc; dispatch; and cabin crew remained very active yet manageable which was critical in managing our situation.

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Original NASA ASRS Text

Title: A Boeing 737 crew reported a loss of pressurization while flying on an oceanic route. They performed the appropriate emergency checklists while descending to a safe altitude; and successfully diverted to a suitable airport.

Narrative: We briefed with the crew that brought our airplane on weather and turbulence. They advised us that the flight previous to theirs a 'Bleed Trip Off' had been encountered and logged in the forms but that they had no issues with that system. I reviewed that write-up during ground ops. We had a routine takeoff. Approximately 25 minutes into the flight we observed a Bleed Trip Off indication. We applied the QRH procedure which lead to shutting down the left PACK. AT this point we still had ACARS capability so I contacted the dispatcher and asked him to get maintenance on the line with us. I briefed them on the bleed trip event and then queried further whether they knew of any altitude restrictions with a PACK shut down. The bleed trip procedure had no altitude restrictions included. With no restrictions noted we continued to our assigned altitude of FL380 which was the smoothest ride. For about an hour the flight went well with no issues and the cabin altitude remained steady. Approximately [hour and a half] into the flight we got a cabin altitude warning along with the warning horn. We saw the cabin altitude at about 11;000' as we executed the immediate action items. We began the turn away and descent procedure from the diversion guide and once established completed the emergency descent checklist. As we continued with the descent we noted that the cabin altitude remained near the 11;000' mark and as we descended through the high 20's the cabin started slowly coming down. We were able to contact ARINC and alert them of our location and descent procedure. They soon patched us in with dispatch and we advised him of our situation. As we got below the track system we began a turn towards the East coast of Florida and began looking for an appropriate airport to recover to. I advised the flight attendants of our situation and gave a TEST briefing. The cabin masks did not drop as we never got above 11;000' cabin altitude. As we descend through approximately 20;000' the cabin altitude was below 10;000' and slowly coming down. We decided to level at 14;500' where we observed the cabin to be steady at 6;000'. Discussions with dispatch lead to an agreement that [an alternate] was the best recovery option given weather; distance; and passenger accommodations. As the aircraft condition was now stable we coordinated the recovery and requested no emergency vehicles. Throughout the very busy scenario; communication between myself and first officer; ARINC; dispatch; and cabin crew remained very active yet manageable which was critical in managing our situation.

Data retrieved from NASA's ASRS site 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.