Gulfstream iv flight crew reported loss of cabin pressure and having to divert.

Attributes
ACN	1660630
Time
Date	201906
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Gulfstream IV / G350 / G450
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Air Conditioning and Pressurization Pack
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Flight Instructor Flight Crew Instrument Flight Crew Multiengine
Experience	Flight Crew Last 90 Days 86 Flight Crew Total 6186 Flight Crew Type 1359
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 100 Flight Crew Total 11600 Flight Crew Type 3500
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Procedural Clearance Flight Deck / Cabin / Aircraft Event Smoke / Fire / Fumes / Odor

Narrative:

Event was while in cruise flight. We were level at FL410 when we asked ATC for clearance to FL430 due to weather in front of us. While reaching FL430; noticed my ears popping. Immediately saw cabin was climbing. Checked pressurization panel and everything was set up correctly. Asked for altitude lower than FL410 while running checklist but unable to maintain pressurization as cabin kept climbing. Kept requesting lower. Emergency checklist popped up on EICAS screen and started running this emergency checklist when we smelled a very strong burning odor. First officer checked in the back for potential fire; and no issues found. Looked at the bleed panel and left bleed showing 0 psi. [Advised ATC] for loss of pressurization and requested 10;000 feet. ATC had a hard time hearing us as we were both on O2 masks at this time. Another plane relayed message and we were granted lower descent. Left bleed valve circuit breaker found popped. Diverted to ZZZ1. Passengers were not happy; but safety first!

Original NASA ASRS Text

Title: Gulfstream IV flight crew reported loss of cabin pressure and having to divert.

Narrative: Event was while in cruise flight. We were level at FL410 when we asked ATC for clearance to FL430 due to weather in front of us. While reaching FL430; noticed my ears popping. Immediately saw cabin was climbing. Checked pressurization panel and everything was set up correctly. Asked for altitude lower than FL410 while running checklist but unable to maintain pressurization as cabin kept climbing. Kept requesting lower. Emergency checklist popped up on EICAS screen and started running this emergency checklist when we smelled a very strong burning odor. First Officer checked in the back for potential fire; and no issues found. Looked at the bleed panel and left bleed showing 0 PSI. [Advised ATC] for loss of pressurization and requested 10;000 feet. ATC had a hard time hearing us as we were both on O2 masks at this time. Another plane relayed message and we were granted lower descent. Left Bleed Valve circuit breaker found popped. Diverted to ZZZ1. Passengers were not happy; but safety first!

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.