On July 8, 1996 at 1604 hours Hawaiian standard time, a Hughes 369D, N64MK, collided with a Mooney M20J, N5801N, while both aircraft were cruising during a formation flight about 10 miles east of the Honolulu International Airport, Honolulu, Hawaii. The Hughes helicopter was operated by Makani Kai Helicopters, Ltd, and the Mooney airplane was operated by Cosmo Flying School, Inc., both located in Honolulu. The aircrafts' flights were performed under 14 CFR Part 91. Visual meteorological conditions prevailed at the time, and no flight plans were filed. The purpose of the flights was to film a television movie. The helicopter ditched in the Pacific Ocean, about 1.5 miles south of Diamond Head. It sank in 150 feet of water and was destroyed. The commercial pilot and three passengers (cameraman and videotape engineers) were rescued, and none were injured. The Mooney was substantially damaged, and it returned for a landing at the Honolulu International Airport. Neither the airline transport pilot nor the two passengers (cameraman and an actress) were injured. Both aircraft had initiated their flights from Honolulu about 1555. An examination of the recovered Hughes revealed the outboard portion of all five of its main rotor blades had sustained impact damage. The tip portion of one blade was severed. An inspection of the airplane revealed the outboard 3 feet of its right wing and a portion of the aileron was severed. (See the photographs and the wreckage diagram for measurements.) According to the Hughes pilot, around 1400 he attended a preflight briefing which included the Mooney pilot and the film crews from both aircraft. The briefing lasted about 30 minutes. Another briefing was held just prior to takeoff. After departure, the Hughes pilot joined up with the Mooney which was passing the Waikiki Beach and was the lead aircraft. The pilots were in radio contact with each other. Both pilots flew their aircraft from the left seat position. The aircraft cruised at 100 knots, about 1,000 feet above sea level. The Hughes pilot reported that he flew together with the Mooney for 2 to 3 miles, and was located on the Mooney's right side and slightly above its altitude. The Hughes pilot further reported that during the formation flight he "felt a strong impact" and then "started to feel strong vibrations." Thereafter, main rotor rpm decreased, the low rotor rpm warning horn sounded, and he autorotated into the ocean. According to the Mooney pilot, she also attended the preflight briefing. During the briefing it was agreed that she would be the lead aircraft in the formation flight. After takeoff, the Hughes pilot joined up with her on her right side. The Mooney pilot further reported that she kept the Hughes in sight, and eventually the helicopter appeared about 20 feet away from her airplane. According to the Mooney pilot, about the time of the accident she diverted her attention away from the Hughes when she pointed out to the actress (in the Mooney's front, right seat) the location of a shoreline hotel. The hotel was visible upon looking through the Mooney's left side windshield. The collision occurred while the pilot was looking in the direction of the hotel. During the formation flight, filming (videotaping) was in progress in both the Hughes and the Mooney. The National Transportation Safety Board reviewed videotapes recovered from both aircraft. The videotapes were several minutes in length and provided both video and audio accounts of the events leading up to the collision. In summary, the videotape showed the closure rate between the Hughes and the Mooney, the ongoing activity in the Mooney seconds prior to the impact, and a partial view of the collision. During the approximate 2-minute period which preceded the collision, the rear seated cameraman in the Hughes was filming the left side exterior of the Mooney. The pictures show the right side of the Mooney, and that airplane appeared to be maintaining a level flight attitude. The Hughes appeared to decrease its distance from the Mooney's right wing and at times appeared several feet higher, lower, in front of, and behind the Mooney. At the instant of the collision, the Hughes was flying abeam the Mooney's right wing in a tight side-by-side formation. In the Mooney, the videotape was taken by the rear seated cameraman while looking in a forward direction toward the front of the airplane. Also, a right side, aft pointing, dashboard mounted stationary camera principally filmed the front of the right seated actress and the front of the pilot. The videotape shows the following events transpired within about 1 minute of the collision: The Mooney pilot appears to notice that the helicopter has varied its altitude relative to her airplane and she comments about it, the pilot looks to the right toward the helicopter, she laughs, she looks left in the direction of the shoreline and states (to the actress) "and over here used to be (sound of impact) (expletive deleted). . ." In the "Aeronautical Information Manual," the FAA provides the following guidance to pilots who elect to fly in formation flight: (1) Separation between aircraft within the formation is the responsibility of the flight leader and the pilots of the other aircraft in the flight; and (2) This includes transition periods when aircraft within the formation are maneuvering to attain separation from each other to effect individual control and during join-up and breakaway. In addition, the FAA's General Operating and Flight Rules specifies that "no person may operate an aircraft so close to another aircraft as to create a collision hazard (14 CFR Part 91.111)."