The Federal Aviation Administration (FAA) mandated SMS for Part 121 operators in 2015. The regulation allowed just over three years for the operators to develop and implement acceptable SMS Programs. The FAA is currently working on mandating SMS for Part 135 operators – charter, commuter, and air tour operators. The number of Part 135 operators are 10 times more than that of Part 121 operators as shown above, highlighting the enormity and complexity of the task as SMS needs to be scaled down to meet the scope of Part 135 operators in order to be effective.
FAA – Notice of Proposed Rulemaking (NPRM): SMS – https://www.faa.gov/newsroom/notice-proposed-rulemaking-nprm-safety-management-systems