Two business associates and I were on the second leg of a three-leg business trip that would carry us from Chino, California, to Las Cruces, New Mexico, to Boulder, Colorado, and then back home. The first leg was one I had made on numerous occasions because my company had several customers in the New Mexico area. To this day I can mentally recite all the navigational aids and waypoints (in order) to get to Las Cruces, El Paso, Texas, or Alamogordo, New Mexico. On an afternoon in late January 2000, after a couple of days of business meetings at White Sands Missile Range, we returned to the Las Cruces International Airport (KLRU). The weather that day at KLRU was beautiful, not a cloud in sight. A telephone weather briefing for our approximately 500 nm trip raised no concerns — clear with moderate winds aloft. There were no forecast weather problems between Las Cruces and Jeffco — the Rocky Mountain Metropolitan Airport (KBJC) in Denver, our destination. When transitioning a busy traffic area such as Denver I usually file IFR, so after lunch and a thorough preflight we departed, having filed for 11,000 feet.