Both aircraft departed Wichita on IFR flight plan in VFR weather conditions. They flew northwest toward their respective destinations, and cancelled IFR about 20 minutes before the accident. ATC observed the airplanes on radar, and stated they were 'dogfighting back and forth' prior to the collision. One pilot's roommate reported the two pilots, who were close friends as well as co-workers, often cancelled IFR and flew in formation if the weather was VFR. He reported the pilots often videotaped each other, and he had watched some of the tapes. He stated 'it was hard to tell from the videotape how close they were because they could use the zoom feature, etc. You could read the N numbers.' Investigation revealed brown paint transfer on the bottom of the right wing of the blue and white airplane, which had separated and was located 1.5 miles from the main wreckage. There were light colored scuff marks on the top of the left engine nacelle of the brown and white airplane.