I've travelled from Vancouver to London often enough to see this phenomenon as something that happens regularly enough to notice. I'm just not sure why.
So... the route from Vancouver to London is basically a series of right-hand turns. I guess it follows a set of rhumb lines or whatever. But what I noticed was that most right-turns are preceded by a smaller left turn.
ie the aircraft banks and turns left for a couple of seconds, then straightens up and goes straight into the longer right hand turn I'm expecting.
So my question is, why does it do that little turn in the opposite direction? I can't imagine it's navigational, not when it's cruising at high altitude. Is it something mechanical? Say to make sure everything is working and not iced up? I imagine the aircraft is on autopilot at that point, so it's not a pilot thing.
Does anyone know what this is? In fact, has anyone else even noticed this?! I think I've noticed it most on Vancouver-London because when you're over Iceland and the aircraft starts to turn north, you start to wonder where you are headed!