The East is Odd, West is Even Odder
Mike Kelley, “Airportraits”, Tiny Fox Lab

Air traffic controllers direct commercial flights to fly at “even” or “odd” levels. The general rule in most parts of the world is aircraft going east will fly at odd levels, i.e. 35’000 feet, while aircraft heading west will fly even levels, i.e. 34’000 feet.Tiny Fox Lab Facts

Preview photo credit: Mike Kelley, “Airportraits”
Source: thepointsguy.com/guide/…