This May 2009 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.
Aircraft: Cessna 172, Cessna 310. Injuries: 3 Fatal. Location: Long Beach, Calif. Aircraft damage: Destroyed.
What reportedly happened: The Cessna 172 and a Cessna 310 were both flying in the local practice area in VFR conditions. A CFI and student pilot were aboard the C-172. The CFI had 1,880 hours, while the student had 3.7 hours. The C-310 pilot, who held an airline transport pilot certificate, had 3,070 hours.
A pilot in another airplane was flying on a southerly heading within the immediate area of the collision and noticed a silhouette of an airplane, which appeared to be a Cessna 172 at his 10 to 11 o’clock position. The airplane appeared to be performing maneuvers and making turns in a counter-clockwise direction, followed by a turn in a clockwise direction. The witness noticed another airplane — later determined to be the 310 — entering the area from the west, traveling at a high rate of speed on an easterly heading. He was unable to see what kind of airplane it was and only saw a “black object” due to the sun being almost on the horizon. The witness continued to watch both airplanes and noted the fast moving airplane was continuing on an easterly heading while the Cessna 172 was still performing maneuvers on a southerly heading around the same altitude. The airplanes collided and fell to the ocean.
The witness contacted local air traffic control to report the collision and continued to circle the area of floating debris until first responders arrived. During examination of the recovered wreckage, transfer marks were identified consistent with the radar-derived collision angle. Both airplanes were operating under visual conditions when they collided.
Probable cause: The failure of both pilots to see and avoid each other’s aircraft.
For more information: NTSB.Gov
These were a lot more instructional when they linked to the NTSB reports, e.g., on this one I wanted to go look at the factual to see what time of day the accident occurred. While it’s possible to find them, it would be nice if you’d include the NTSB accident # in the story.