On February 1, 1991, a Boeing 737 landed on top of a Metroliner holding on runway 24L, killing 34. A part of the accident was a perception issue. Experiments were done which proved that if a pilot expected to see an airplane where it was that night, he saw it. If he didn't, he didn't. The crew of the 737 did not expect the Metroliner, and so flew right into it with open eyes. We see what we expect to see, and not what we actually see.

In ep.10 (or so) of Lucky☆Star, we get to peek into Izumi's family scrapbook, and this is what I saw:

A day or two later, I was reading an entry at AoMM and saw:

Konata inherited her father’s mole? How do you pass on a mole?

"Looks more like her mother's mole", I thought. But before posting a comment, I pulled out a shirt from a closet, to check how it was buttoned, and...

At least my error of perception didn't kill 34 people.