SOB

SOB is the total number of people aboard an aircraft at any given moment: pilots, crew, and passengers combined. It appears on flight manifests, weight and balance sheets, and emergency documentation. In aviation maintenance and operations, SOB is the figure that determines evacuation procedures, oxygen supply requirements, and emergency response planning. A regional turboprop with an SOB of 45 requires different protocols than a widebody with an SOB of 350.

The maintenance technician encounters SOB in several critical contexts. Weight and balance calculations must account for the total human load; an aircraft certified for a maximum SOB of 180 cannot legally carry more, even if cargo capacity remains. Oxygen system capacity is tied directly to SOB: a 90-minute oxygen supply must be sufficient for every person aboard in the event of pressurization failure. Life raft and evacuation slide provisioning follows SOB requirements mandated by airworthiness standards.

SOB also drives maintenance intervals and inspections. Cabin pressure systems, emergency lighting, and life support equipment are certified and tested based on maximum SOB ratings. An aircraft that has been retired from passenger service and converted to cargo carries zero SOB, which exempts it from passenger safety system checks but may require different structural compliance.

The term is strictly numerical and administrative rather than operational. Crew planning, fuel calculations, and takeoff performance all depend on accurate SOB data provided to the flight crew. Discrepancies between the manifest SOB and actual passenger count create serious regulatory and safety issues; maintenance records must reflect the aircraft's certified maximum SOB, not a particular flight's count.