Software catastrophe myths

[snopes]

Comment: I live in Australia, and work in computers. There are a few computer
horror stories we have heard (at least 10 years ago) which are used to
drive home the point of bad programming. I think they are Urban Myths,
but a friend thinks they are real.

1. Error 21. A machine used to give radiation treatments to cancer
patients started displaying 'Err21' during operation, but the process
seemed to complete normally. The technicians ignored the error until
people started dying from radiation poisoning.

2. Inverted flight. An updated software in a aeroplane (generally
believed to be a fighter plane) was being tested by the US Air Force.
When the plane flew across the equator (from the Northern Hemisphere to
the Southern Hemisphere), the autopilot software inverted the plane. When
the pilot righted the plane, the software informed him that he was flying
upside down. When the pilot crossed back over the equator, everything
returned to normal.

3. Flight path. In New Zealand an airline company offered a scenic
tourist flight. The path was entered incorrectly into the autopilot. The
pilot reported that the incorrect flight was actually better than their
intended path, but that in one place the altitude should be lowered as it
would create a stunning flight between two mountains. This was done and
the new flight path was a success. After some time a person noticed that
the flight path used by the tourist flight was different from the original
intended flight path and so updated the path without changing the altitude
settings. On the next flight, the plan flew into the side of a mountain
and killed everyone on board. As a side issue to this story, I remember a
tourist flight in New Zealand crashing into a mountain which happened
around 20 years ago, this is the flight generally linked to this story.

One of the reasons I think these stories are Urban Myths is that my friend
is very short on details which could be used to verify the stories, and
when I have talked to other computer people who have heard of them, they
also don't know any details. On the other hand, my friend is married to a
person who works in a hospital and she has heard the first story (error
21) from her work as well.