I believe that when you do something, you should go all-in: AY
666 to
HEL, on a
Friday the 13th, seated in row—of course—
13,
middle seat, checkin sequence number
1. Also bought some champagne to celebrate (to get a receipt showing AY666 ;-)
Sadly AY has since renumbered their flights and no more AY666. There is probably a interesting story somewhere about flight number assignment, as AY666 was a flight from AY big competitor SK's large hub at CPH, maybe they were thinking "a flight from competitor hub, let's number it 666"...
Had very fun discussions with the other aviation geeks and FT people in row 13 ;-) The gate staff was somewhat festive and happy to reprint my boarding pass on official paper stock.

This is great. Shame the gate wasn't A13 though....