A retired P-51 Mustang sits on the Kentucky Air National Guard ramp in Louisville, Ky., April 19, 2012. The Kentucky Air National Guard Base will once again serve as the launching pad for military aircraft slated to appear in this weekend's 22-annual Thunder Over Louisville air show. This year's schedule features more than 25 current military planes and helicopters from the U.S. Armed Services and Canadian military, as well as variety of historic war birds. Highlights include the F-22 Raptor, a B-2 Stealth Bomber and F/A-18 Hornets.