Flight crew reported loss of cabin pressurization control; resulting in an air turnback.

Attributes
ACN	1705593
Time
Date	201911
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B787 Dreamliner Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Pressurization Control System
Person 1
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 163 Flight Crew Total 7215 Flight Crew Type 2753
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Published Material / Policy

Narrative:

Normal ground ops and departure from ZZZ. MEL item lower recirc fan all other systems normal. After level off at FL330 entering ETOPS; pm noticed cabin altitude at 8600 ft.; steady increase at 100 ft./min. Cabin alt was amber; no other EICAS or cautions. Differential pressure was 6.5. Captain/pilot flying called dispatch/ [technical operations maintenance control]; unable to rectify issue; dispatch concur with air return. Relief pilot recalled to flight deck; pilot monitoring request clearance for return to ZZZ while [relief pilot] ran qrg divert checklist. Captain ran test checklist; briefed approach; flew normal landing.

Original NASA ASRS Text

Title: Flight Crew reported loss of cabin pressurization control; resulting in an air turnback.

Narrative: Normal ground ops and departure from ZZZ. MEL item lower recirc fan all other systems normal. After level off at FL330 entering ETOPS; PM noticed cabin altitude at 8600 ft.; steady increase at 100 ft./min. Cabin alt was amber; no other EICAS or cautions. Differential pressure was 6.5. Captain/Pilot Flying called Dispatch/ [Technical Operations Maintenance Control]; unable to rectify issue; Dispatch concur with air return. Relief pilot recalled to flight deck; Pilot Monitoring request clearance for return to ZZZ while [Relief Pilot] ran QRG divert checklist. Captain ran TEST checklist; briefed approach; flew normal landing.

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.