LAS VEGAS — A plane that crashed into spectators at an air race in Reno last year bore modifications that weakened its structure and showed evidence that it was flown beyond its limits, investigators said Monday.
The National Transportation Safety Board deemed the failure of a tail structure to be the probable cause of the crash of the souped-up World War II-era P-51 Mustang fighter that killed pilot Jimmy Leeward and 10 people on the ground at last year’s National Championship Air Races in Reno and hurt more than 70.
Leeward also was blamed for failing to fully document and test extensive modifications to the aircraft before the September 2011 crash.
Board member Robert Sumwalt said: ‘‘If you want to go out and fly fast and try to win, that’s one thing. . . . If you’re modifying an aircraft without fully understanding how the modifications can affect the aerodynamics, you’re playing Russian roulette.”
Structural modifications of the aircraft made it lighter and reduced drag, according to the NTSB report. But flight control modifications also made the aircraft less stable.