a number of years ago when I traveled frequently for work I was very focused on optimizing my airline miles and points.

At some point as part of a computer system cutover, United Airlines suddenly started shorting people miles on airport to airport differences. Not a lot, but a few here and there. A group of folks on flyertalk slowly realized that the change was perfectly explained by the difference between treating the globe as a perfect sphere and treating it as an oblate spheroid.

The previous model had been technically correct and precise. Whoever built the new model had simplified the code for some reason. After much kvetching United fixed it.