Last year’s crash of a modified North American P-51 Mustang, into a crowd of spectators at the Reno National Championship Air Races, claimed the lives of 11 people including the pilot. The aircraft struck the box-seat stands at the south end of the course where 66 more people suffered serious injuries.

In repsonse to this accident, NTSB last week released a number of recommendations after reviewing and uncovering a number of inconsistencies contained in air-race guidance publications, FAA Order 8900.1 and AC 91-45A. The safety watchdog found “Numerous discrepancies, errors, and instances of outdated information that undermined their purpose.” In some places, documents contradicted each other.

The NTSB wants the FAA to revise the Order and the Advisory Circular to correct “inaccurate and incomplete information and reconcile all differences and inconsistencies between the documents.” For example, although the P-51 was highly modified, the aircraft was not subject to the National Air Racing Group Unlimited Division’s rules concerning additional design and test criteria.

As the NTSB continues to review how the modifications may have altered the aircraft’s handling characteristics, it recommends, “As a condition of eligibility to participate in the Reno National Championship Air Races, [owners] provide an engineering evaluation that includes flight demonstrations and analysis within the anticipated flight envelope for aircraft with any major modification, such as to the structure or flight controls." Additional recommendations include reevaluating safety areas to more effectively avoid spectators, provide high-G training to some pilots and demand G-suits for some pilots where feasible.