My wife and I witnessed 4 amber/orange red lights directly south of our Gilbert Home on Monday (April 28 2014) evening. The lights seemed to be traveling from west to east over the San tan mountains viewed from our location. As a pilot I knew these weren't conventional aircraft due to the light color and configuration. We watched as they flew in formation for about 10 - 15 minutes then the lights seemed to flicker and fade out. The lights seemed to be away in the distance so no sound was observed.