The Aircraft Owners and Pilots Association (AOPA) is calling on the National Transportation Safety Board (NTSB) to conduct an internal review to examine why the independent safety agency has approved “speculative probable cause reports related to general aviation accidents” despite little evidence to support the conclusions.

AOPA Senior Vice President of Government Affairs Jim Coon criticized speculative practices that seem to be finding their way “into the culture of NTSB.” He objected to probable cause findings of medical incapacitation that have appeared in accident investigations, “contrary to other compelling evidence,” in a letter to Bella Dinh-Zarr, the NTSB’s acting chairman. Dinh-Zarr assumed the NTSB’s leadership post on the expiration of Christopher Hart’s term as chairman March 15.

AOPA is concerned that in some cases the NTSB is relying less on facts and more on speculation. Several recent probable cause findings raise concern about an erosion of data-driven, facts-based standards that have long given NTSB accident analyses credibility, Coon wrote.

“Personally, after having worked with the NTSB for decades, it is disheartening that the Board is now allowing someone at the staff level to approve these academic probable cause determinations. Moreover, I am dismayed that the Board’s Chief Medical Examiner allows this speculative practice to continue.

“We hope the Board would work towards a more data driven approach similar to that which the FAA has embraced, and more specifically the Flight Safety Standards Division. Together, we have invested significant time and effort to move to a data driven approach under the Commercial Aviation Safety Team (CAST) and the General Aviation Joint Steering Committee (GAJSC),” he wrote.

An internal review could correct the problem of speculative probable cause determinations, he said, and ensure that “personal agendas in the medical office are not being incorporated into the Board’s reports.”

Read AOPA’s story.

About AOPA – Since 1939, AOPA has protected the freedom to fly by creating an environment that gives people of all ages the opportunity to enjoy aviation and all it has to offer. As the world’s largest community of pilots and aviation enthusiasts with representatives based in Frederick, Md., Washington, D.C., Wichita, Kans., and seven regions across the United States, AOPA’s events, initiatives, and services bring current and future pilots together and make aviation more accessible to everyone. To learn more, visit