The Air Charter Safety Foundation (ACSF) recently completed its Industry Audit Standard (IAS) for registered Part 135 and fractional jet operators, a segment that flew 616,777 flight hours between 2009 and 2013. The audit identified a single ground event during that period. IAS-registered Part 135 and fractional jet operators experienced an accident rate of 0.162 accidents per 100,000 flight hours, according to ACSF and NTSB accident data. For all other Part 135 and fractional jet operators during the same five-year period, the accident rate was 0.54 accidents per 100,000 flight hours.