I was looking at pics of FMCs earlier and I noticed that on one, the keyboard has several letters with white box lines, such as:
Photo © Craig Murray
while others do not:
Photo © Daniel Werner
Is there any particular reason or function for this? It seems to be a recent feature, so which aircraft have it?It's not a big deal, it just seemed interesting and my curiousity was piqued, lol. Thanks for any help, guys.