Cessna Citation Sovereign (C680)
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 230; Flight Crew Total 29241; Flight Crew Type 850
Time Pressure
Aircraft Equipment Problem Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Clearance
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Returned To Departure Airport; Flight Crew Landed in Emergency Condition; Flight Crew Diverted
Aircraft
On reposition flight to ZZZ1; climbing through FL250; had Amber CABIN ALT CAS message followed shortly thereafter with Red CABIN ALT message. (Checked Pressurization gauges and abnormal checklist while descending). Leveled off and requested immediate descent which was approved. Rapid descent to 13;000 feet followed by return to ZZZ for maintenance on this aircraft. (Center provided priority handling; but we said it wasn't necessary).
CE680 Captain reported a pressurization failure resulted in an expedited descent and a diversion.