I know that several crashes in which the plane was entirely or almost entirely obliterated into small fragments have been pointed out. I discovered one more. This also MAY have been the 1st time an American plane was taken by force and the first instance anywhere of a suicide ‘hijacker’.
The Crash of Pacific Air Lines Flight #773
(Near San Ramon, Calif.) May 7, 1964
A Different Time...
The year was 1964. It was a time when getting aboard a commercial airliner was much easier than today. You paid your money, walked through a gate (then often across the tarmac) and boarded the plane. No X-rays, no security check points, no guards. The wave of hijackings to Cuba was still to come, only to be followed by terrorists hijackings and even worse beyond that.
It was a time when we all thought nobody was crazy enough to take a gun aboard a airliner and threaten to kill people, let alone actually shoot someone. Well on Pacific Air Lines Flight 773, that's exactly what happened.
According to newspaper accounts of the time, Francisco Gonzales would constantly threaten people, especially members of his family. He said that they would die alongside him, by his hand.
But what brought about his problems? Gonzales, 27, had been a member of the Philippine yachting team at the 1960 Olympics. However, by 1964 he was having trouble with his wife and also had accumulated a fair amount of debt...on the evening of the May 6th, Gonzales purchased a Smith and Wesson .357 magnum from an acquaintance.
[...]
Gonzales went to the airport, and boarded the plane which was headed first for a stop in Stockton, then on to San Francisco. According to witnesses who got off the plane in Stockton, Gonzales was seated right behind the cockpit door...about the time the Fairchild F-27A (N2770R) with 43 other souls aboard, started to descend for its landing, Gonzales pulled out his gun and kicked his way into the cockpit. Once in there, he raised the gun and put a bullet into the back of the pilot's head. Ernest Clark, 52, was dead. At 6:48 the aircraft radioed its last message. First officer Raymond Andress was heard saying, "Skipper's shot. We've been shot. Trying to help." There were more shots as Gonzales turned to the co-pilot and shot him.
The twin-engine plane went into a steep, uncontrolled, high speed descent to crash into a hill and explode near San Ramon early in the morning of May 7, 1964. All 44, 41 passengers and 3 crew members, were dead on impact.
There was a large crater with debris spread over a very large area. In the wreckage, along with personal belongings, a bible and papers, investigators found the .357. All six shots had been fired.
The Crash Site Today
According the Civil Aeronautics Board report, the aircraft struck the up-slope of a 25. 2 degree hill at a relative angle of 90.2 degrees. The wreckage was confined to the east slope of the 800 foot hill and strewn 1,050 feet up the slope along a 800 foot width from the main crater. The cockpit area was so completely destroyed by impact that only four small pieces of the instrument panel were retrieved. No single portion of more than eight square inches was recovered.
http://www.check-six.com/Crash_Sites/PAL_Flight_773_crash_site.htm
It should be noted that the plane probably impacted the ground with less velocity than any of the 9/11 crashes and was far less massive. The 27A had a max cruising speed of 294 mph [473km/h (255kt)] and a max takeoff weight 20,639kg (45,500lb) [10,398kg (22,923lb) empty] and thus would have had far less energy to fragment the plane
http://www.airliners.net/aircraft-data/stats.main?id=217
