> 3) winds are generally faster the higher you go so you'll usually go about at high as you're able, at least in one direction.
I recently flew from NYC to Lisbon, Portugal and it was 6.5 hours there (flying east) and 7.5 hours back (flying west) because you go with and against the jet stream.
I wonder if there's a noticeable difference if you fly at a lower altitude against the wind. It didn't seem like the plane adjusted for that, it cruised at the same altitude both ways from what I remember. Both flights used the same exact plane type (A330neo).
