I've had a look through the forums for this topic, but obviously it's hard to wade through hundreds of threads with "calibrate" in them.
A while back I was having a go in the training arena, and the bombsight calibration procedure had changed. Instead of simply pressing U and Y, I had to point the bombsight at a spot on the ground for a few seconds in order for the calibration to fix. This is a bit more involved than the current procedure, and also a bit more involving.
I can only assume that bombsight calibration has evolved over the years that Aces High has been online, and that an older system was being tested out when I was in the TA. The current system seems perfunctory - you press one key, press a second key, wait, and then let go - although I imagine that there are fewer people asking for help on the help channel because of it (instead, they all want to know how to fire rockets).
Is there a reason calibration was changed? I prefer the older system, as it introduces an element of skill to what is otherwise a mechanical act.