Learjet 35 captain reported diverting during the climb phase due to a cabin pressurization problem.

Narrative:

Upon departure from lax I personally noticed that there was a significant amount of pressure in my ears and sinus cavities. I was at the time of this incident; in the middle of a cold; which I mistakenly identified as the source of the pressure issue. I neglected to check the cabin pressure due to the pain I was experiencing which is part of the after takeoff check list.passing through 10;000 feet; we received the cabin altitude warning. We started to run through the associated checklist but could not complete the checklist in its entirety because we decided it would be best to land. We safely landed the aircraft and the crew and passengers exited the aircraft. We found that after maintenance; the bleed air switches were placed in the off position which appeared to me; because or the angle during the expanded checks; to be in the on position because they are always in the on position and almost never placed in off. Obviously; the mistake was my neglect to catch it during the expanded checks. The switches were placed on and we completed the flight safely.

Original NASA ASRS Text

Title: Learjet 35 Captain reported diverting during the climb phase due to a cabin pressurization problem.

Narrative: Upon departure from LAX I personally noticed that there was a significant amount of pressure in my ears and sinus cavities. I was at the time of this incident; in the middle of a cold; which I mistakenly identified as the source of the pressure issue. I neglected to check the cabin pressure due to the pain I was experiencing which is part of the after takeoff check list.Passing through 10;000 feet; we received the cabin altitude warning. We started to run through the associated checklist but could not complete the checklist in its entirety because we decided it would be best to land. We safely landed the aircraft and the crew and passengers exited the aircraft. We found that after maintenance; the bleed air switches were placed in the off position which appeared to me; because or the angle during the expanded checks; to be in the on position because they are always in the on position and almost never placed in off. Obviously; the mistake was my neglect to catch it during the expanded checks. The switches were placed on and we completed the flight safely.

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.

Attributes
ACN	1389009
Time
Date	201609
Local Time Of Day	1201-1800
Place
Locale Reference	LAX.Airport
State Reference	CA
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Learjet 35
Operating Under FAR Part	Part 135
Flight Phase	Climb
Route In Use	SID GORMAN6
Flight Plan	IFR
Component
Aircraft Component	Indicating and Warning - Air Conditioning and Press.
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Less Severe Deviation - Procedural Published Material / Policy