Originally Posted by
florens
What you refer to is cruising Flight Levels, I believe, though they are not the same everywhere. It‘d be inverted actually. Eastbound odd, westbound even.
nah definitely flight numbers (as well)
it may be a complete urban myth but even/odd north/south east/west or whatever is fairly extensively referenced (with the qualifier that some airlines ignore the tradition)
e.g.
https://www.businessinsider.com/what...8-3/?r=AU&IR=T