A World War II-era plane that crashed into a stadium killing nine had radical changes in order to compete in the National Championship Air Races in Reno on September 16, according to the Associated Press.

The 65-year-old P-51 Mustang, named Galloping Ghost, was rebuilt for speed and maneuverability to compete in the air show. Changes to the aircraft included the removal of 10 feet of wingspan and ailerons (back edges of airplane wings used for balance) cut in half.

The plane was piloted by veteran stunt pilot Jimmy Leeward, who was seen on a June 2011 YouTube podcast admitting his uncertainty about the modifications.

I know it'll do the speed, said Leeward in podcast. The systems aren't proven yet. We think they're going to be OK.

The aircraft nosedived into VIP seating at the Reno air show killing nine spectators.  An additional 69 spectators were treated at a local hospital. On Sunday, 36 were released with an additional six in critical condition. This is the first time spectators have been killed in the 47-year history of the race. However, 20 pilots have lost their lives.

Hysteria broke out in the crowd when the plane headed for the grandstand. In that moment, Noah Joraanstad, a 25 year-old Alaskan commercial pilot, believed he was going to die. Joraanstad survived the crash and was among those treated.

I think I was very, very fortunate. I thank God for it, the shrapnel that hit me, hit me right in the right spot where it just missed all my important organs and arteries and my spine, Joraanstard told ABC News.

Investigators are still working to identify what caused the crash, although it is believed that a piece of the tail, known as the elevator trim tab, may have been missing prior to the incident.

The National Transportation Safety Board will also investigate the black box, memory cards, and forward-facing video camera recovered from the crash for clues as to why Leeward couldn't regain control of the craft.