LAS VEGAS (AP) - A highly modified vintage aircraft was pushed beyond its structural limits before it crashed into spectators at last year's National Championship Air Races in Reno.
That's among the findings being presented to the National Transportation Safety Board on Monday in Washington.
Loose screws on a crucial tail assembly are also blamed in the September 2011 crash that killed 74-year-old pilot Jimmy Leeward and 10 people on the ground and injured more than 70.
This year's Reno Air Races start Sept. 12.
The five-member NTSB has already issued several preliminary reports and recommendations for the Federal Aviation Administration and race organizers to improve safety.
NTSB officials say Leeward's World War II-era P-51 Mustang fighter reached 530 mph before it pitched skyward and then slammed nose-first into rows of box seats.