Thanks for the replies, guys.
So...in short, there's no real rationale for the button, it's just a score quirk that tests out if you pre-flight...forget to click a button and ruin your score...how does this relate to a simulation????
Fuel selection is buggy? Don't rely on the GUI, use unix style dot commands?
I do so hope that AH doesn't go the same way as AW (I'm sure it won't

), lot's of new stuff, but original bugs left unfixed.....