Last season, all teams wore a flag patch on their caps on September 11. This was what MLB did following the aftermath of the attack in 2001.
It was announced by New Era that they are doing that again.
I actually am a fan of this. This is simple, not a gimmick like other things MLB does, and more importantly, it takes us back to when MLB first reacted towards the attack. Simple and very honorable.
(Although I am confused as to why they have old cap designs with it. It must just be extra in inventory and they slapped on the flag onto it for merchandise sales.)