Originally Posted by
aster
Does "F" on AY mean a business class seat (via upgrade) by any chance?
Originally Posted by
esledo
Yes, it means just that.

Indeed:
[KVS Availability Tool 7.3.4/Diamond - Seat Map: 01 Mar 2014/AY 5/HEL-JFK/333/F-Business]
Code:
A C | D H | L
1 - - - - -
2 - - - +
3 - + - - -
4 - - - -
5 + - - - +
6 - - - -
7 + + + - +
[+] Available [W] Wing [L] Lavatory
[-] Unavailable [E] Exit Row [U] Upper Deck
[P] Preferred [|] Aisle