blocked seats

When looking at sear allocation on expert flyer.com. there were 4 seats in UC that were 'blocked.' What does this mean please?

[Decker]

Kept for subsequent release.

thanks decker, but could you please tell me why they do this? Thanks

[Decker]

To ensure they can accommodate family groups (who haven't prebooked seats) who have to be seated together if possible.

Thanks, so have these seats been sold?

[Decker]

If blocked then in theory some of them would have. So projecting as to the reason for the question, the available seats on any given flight are basically the ones that aren't blocked or allocated give or take a few. That having been said SOME carriers block seats to that their Frequent Flyers can choose them. Under these circumstances the seat may not have been sold and would be freed up later. In addition certain seats are blocked because they are the only ones that can accommodate bassinets and the airline doesn't know if there will be a last minute 'baby booking'. It's never straightforward is it?