I've been told anecdotes like this several times on the interviews. Interviewers used this story as an argument in favor of defensive software development.
Here is an explanation from one of the numerous occurrences on the web:
This story was told by people from Motorola and is supposedly included in every microcontroller training course Motorola gives.
Test flights of F-16's were being conducted in Israel. The F-16's were doing low height rounds. On approach to the Dead Sea, the whole navigation system suddenly reset itself. The daring pilot landed the bird. HQ called up Motorola and ordered a team on the spot ASAP. The ground tests went perfectly, but every time the bird went airborn, it rebooted.
The pilots were getting restless. Flying on the border of hostile territory without navcom, with the Arabs pointing their earth-to-air missiles at anything that moves, wasn't that pleasant. Neither was debugging the whole navcom in-flight. Then someone figured it out.
The height of the Dead Sea relative to world sea level is -400 meters. As soon as the F-16 reached sea level, the navcom did a divide by zero, crashed, and rebooted.
When I tried to search for information on this topic I couldn't find out any references to mentioned Motorola training courses. I also failed to find any references to real-life events (dates, places, crash reports).
My question is: Were there any documented cases of aircraft navigation system crashes due to zero/negative height level?
Additional question that emerges from the quote above: Are there any Motorola microcontroller training courses that mention "Dead Sea case" as an example?