January 19, 2012 at 9:15 am
On January 18, 1982, during a training flight four of Thunderbirds T-38 Talon aircraft crashed at Indian Springs, Nevada. The diamond performed loop in a line abreast, when the leader’s plane received mechanical failure, which does not allow it to exit from loop.
Source: http://aerobaticteams.net/news/thunderbirds-diamond-crash-30years.html