Thread: HK's

There are a lot of seats with Delta that you either have to be an elite passenger to select in advance, or you have to pay additional to select in advance, because they are considered "premium seats" (Any aisle or window in the forward half of the cabin.) Likewise, they hold a certain number of seats for assignment at the gate.
Basically, what this means is that if a flight is anywhere near full, there are always going to be a number of people with confirmed tickets on the flight, yet who do not yet have a seat assignment. Those are the HK's you are seeing.
The reason you don't see them until a few hours before the flight is because until they actually check in, they will not show up on the ASL (Airport standby list)
Always, always, always go by the "flight list" you speak of. The standby list that shows 5 seats open, doesn't actually show 5 seats open. It just means there are 5 seats unassigned, although they have been purchased by a confirmed passenger.