B757-200
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Situational Awareness; Troubleshooting
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Landed in Emergency Condition; Flight Crew Diverted
Aircraft
In the climb to 35;000 feet passing 30;000 feet we received a Cabin Altitude warning. The FO (First Officer) and I went on 100% oxygen and silenced the warning. We began a descent and [requested priority handling] for loss of cabin pressurization. The cabin altitude indicated approximately 15;000 feet. We were initially cleared to 24;000 feet; then 16;000 feet; and then 10;000 feet without any intermediate level offs. I directed the FO to begin the descent while I ran the QRH (Quick Reference Handbook) for cabin altitude and for automatic pressure system failure. Upon leveling at 10;000 feet it appeared that the manual system was able to pressurize the aircraft and the cabin pressure had been decreased to approximately 4;000 feet. At this point we coordinated with Dispatch for fuel calculations; NOTAMs and weather to formulate a plan. The FO and I decided to climb to 25;000 feet and attempt to continue on to ZZZ. Upon passing 21;000 feet the manual system did not seem to be able to maintain pressurization and the cabin altitude increased to approximately 8;000 feet and climbing 700 feet per minute. We decided to descend back to 10;000 feet and to divert to ZZZ1 based on coordination with Dispatch. We then completed the QRH checklists and prepared for the approach and landing.
B757 flight crew reported loss of cabin pressure during climb to cruise; resulting in a diversion.