June 30, 1956....commemorated today at the Grand Canyon

[Bartman]

In the days leading up to this accident, the atmosphere was probably very similar to what we're seeing today.

http://www.nps.gov/grca/parknews/1956-nhl-designation.htm

and another

http://www.aopa.org/News-and-Video/All-News/2014/May/02/midair-spurred-modern-atc.aspx