On May 10, 2008, at 1300 Pacific daylight time, a Moravan Zlin 50LX, N6660K, collided with terrain while performing at the Modesto Air Show, Modesto, California. The commercial pilot, who was also the registered owner of the airplane, was operating it under the provisions of 14 Code of Federal Regulations Part 91. The pilot sustained serious injuries, and the airplane was substantially damaged. Visual meteorological conditions prevailed, and no flight plan was filed. The flight departed about 1245. Two Federal Aviation Administration (FAA) inspectors acting as the FAA monitors, witnessed the accident. During the accident pilot's performance, the pilot was transmitting directly to the crowd, as well as communicating with an on ground safety observer, the airshow waiver holder, and an air traffic control tower controller. The pilot had completed a normal sequence and then added an additional maneuver. The FAA inspector indicated that during the added maneuver, the right wing impacted the ground. Additionally, the FAA inspector indicated that the airshow is conducted at a controlled field serviced by airlines. Performances, as a rule, are timed so that they do not conflict with inbound and landing airline traffic. If there is a timing conflict, normally the show is temporarily stopped so as not to delay the airline traffic. In the pilot's written statement, he indicated that during the airshow briefing, he and others had requested a sterile frequency for maintaining communication with airshow and ground support staff, which he indicated was standard operating procedures at other airshows. The air traffic control tower personnel elected to have the airshow pilots monitoring and communicating on the same frequency as the tower controllers. The pilot stated that during the flight, he was interrupted numerous times by tower personnel and incoming aircraft, which prevented his ground safety observer from communicating with him. He continued by stating that near the end of his routine, while performing rolls at a low altitude, he received, "...unanticipated, reckless, and urgent directions to immediately leave the airshow area in mid-maneuver." He advised the tower controller that he had too much energy to follow their instruction. He then stated that at a, "...critical point later in my maneuver, the tower then carelessly directed me on an urgent basis to go straight out of the airshow box. This combination of events, including but not necessarily limited to the mid-maneuver situation, the lack of a sterile frequency...and the directions from the tower...resulted in further disorienting me to a point that I hit the ground." The FAA accident coordinator transcribed the communication between the pilot, the airshow waiver holder, the safety observer, and the tower controller. The transcript showed that during the pilot's performance, an airliner contacted the tower to land. The airliner reported that they were 5 miles from the airport, and the airshow waiver holder told the accident pilot that an airliner was 5 miles from the airport and that, "...this will be your last one." Then, the tower controller contacted the pilot and advised him to make a right base entry for landing on runway 28 right. The pilot requested to make one more pass and the tower controller approved the request. The pilot affirmed. The airliner then landed and was told to contact the ground controller. The tower was then contacted by ground operations requesting to cross a runway to the accident site. According to the Modesto airshow waiver holder, prior to the show all pilots are given a briefing from the airshow waiver holder, FAA personnel, and air traffic control tower personnel. During this meeting the frequency was discussed, and tower personnel elected to have the pilots on the tower frequency. According to the airshow waiver holder, during the accident flight, both he and the tower controller advised the accident pilot that an airliner was inbound to the airport. According to the waiver holder, the pilot requested with the tower controller to perform another pass and then collided with the ground during this maneuver.