I've been meaning to knock one of these up for a while, and finally got around to it - a ready reference guide to speed and alt conversions - can be self-supporting or blue-tacked to the side of the monitor. Now when Oberon states he's at 3500' and 240 mph over Dover I'll not be milling around at 4000m and 300 kph wondering why I can't see him in my 109's gunsight.
Of course, I could just wait for the inevitable spin and after about a minute or so he'd appear, disappear, appear, disappear...