The overall number of civil aviation accidents declined significantly between 2012 and 2013, according to NTSB data published earlier this month. However, bucking this trend were Part 135 operations, for which the number of accidents doubled during the same period.

“It’s important to distinguish the Part 135-operated business jets’ safety record from the overall Part 135 accident rate, which includes medical services, air tours and other specialized operations,” said Bryan Burns, president of the Air Charter Safety Foundation, a group focused on maintaining a high level of safety among Part 135 charter and fractional operators.

Burns analyzed some of the NTSB data for AIN. “U.S.-registered business jets operating under Part 135 using nonscheduled certificates for passengers or cargo were involved in only three nonfatal accidents in 2013,” he said.

Part 135 on-demand air-taxi operators of all aircraft types were involved in 45 accidents in 2013 versus 36 accidents in 2012. The number of fatal accidents increased to 10 last year from eight in 2012.

“We estimate that with three million hours flown, the overall accident rate is 1.50 accidents per 100,000 hours, and the fatal accident rate is 0.33 accidents per 100,000 hours,” concluded Burns. Those numbers do reflect an increase over 2012, when the non-fatal accident rate was 1.24 per 100,000 hours, and the fatal accident rate was 0.28 per 100,000 hours.