flickr.com — Photo snapped by Eric Harrison on 21 June 2009 at the St. Thomas Air Show 2009 in Ontario, Canada. This transonic CF-18 Hornet is flying slightly below Mach 1. The Prandtl-Glauert Condensation Cloud, also called a Prandtl-Glauert Cloud or P-G Cloud, is caused by the Prandtl-Glauert Singularity, a fascinating phenomenon of fluid mechanics. (General Sciences)