Something odd to supplement my previous post:
As I wrote, no seat selection fees when we booked in November (PE outbound and return in J). In both cases it was "classic", not "flex". I assumed this was because I'm sky team elite plus and my son is Volare Plus.

Flight out of SFO was just cancelled and we were rerouted via JFK:
- Seat assignment now asking $71 for me (kid is still free)
- For some strange reason, I also lost seat assignment on the return (although kid did not) and it is asking 150€ to get my old seat back, which was aisle.
Gentleman on the phone was able to give me back my J seat for free, but not the PE seat.
Lady on the phone says I should pay because although I had a previous seat assignment, that assignment was free of charge. This even if the reseating is due to IRROPS !! I'm going to dispute the charge when we file for EU261...

Question for the experts: when rerouted via JFK in PE, the SFO-JFK segment on DL was booked in Y. Is this correct ? Shouldn't it have been Comfort Plus ?
That's what DL does: PE segments without PE cabin are C+

Incidentally, this is the second time in 3 attempts that the direct SFO-FCO gets cancelled on the morning of...