Slightly off topic - can't remember where I read the physics of it (possibly Barry Schiff) but do pilots INCREASE their cruise speed when flying with a headwind, and conversely decrease it when flying with a tailwind?
I appreciate certain sectors (NAT tracks for example) where Mach number is part of the clearance and cannot really be altered (?) but I seem to remember it was about trying to maximise the positive effects of a tailwind (and minimise the negatives of a headwind) with regards to total fuel consumption.
Just wondered if this actually occurred?