[steveBK123]

That's an issue, and going from kayak to delta for same flight leads to same issue.

I wonder if this is some bug/edge case for really close in flights? The example flight booking takes off 2 hours from now?

Last time I ever tried to book a flight so close the online sales funnel was closed due to post-9/11 security restrictions. I think 2 hours is about as close as is even legal right?

Can you replicate for a flight tomorrow / next week / next month?

[alwa]

In my experience this replicates routinely for Delta Main Cabin fares for non-elites on leisure/non-corporate travel once only “Preferred Seats” are left in the economy cabin.

What I think the other carriers do well is detect when there aren’t non-charged seats available for advance selection, and remind you that you can continue without paying for a specific seat and still be guaranteed a seat on day of departure.

Delta hand out “free preferred seating” as a perk to all sorts of categories of traveler though. I wonder if that complicates the prospect of offering that kind of warning.

[hanzmanner]

Urgency is one of the key motivators for using dark patterns. Wouldn't be surprised if Delta defaults to "1 seat available at this price" for all busy flights within X take off time regardless of the availability.