I don't understand the OP's question -- are you talking about blocking preferred seat assignments (bulkheads, exit rows, etc.)? Or are you talking about somehow blocking certain fare buckets at certain points in time?

The latter, all airlines do, and are fully within their rights to do, in so far as they think it will make them more money.

The former, I am confused how blocking preferred seats will result in a (presumably customer-unfriendly) conspiracy? If Delta is trying to sell premium seats, it is in their interest to have as many such seats available as possible at all times.


But yes, as others have mentioned, Delta does block certain seats. It is quite easy to figure out which, even without ExpertFlyer -- do a search for flights on a very distant date and look at seat maps. You will notice that certain seats are always blocked even on flights which quite clearly do not have any paying passengers yet. Notably the last two rows of every aircraft (as far as I have seen) and certain seats near the front of the cabin are always blocked until check-in, presumably to allow for some flexibility in accommodating groups, families, people with disabilities, and whatever other special cases may arise.

I have a hard time seeing how there's any conspiracy here -- indeed, Delta blocks some Comfort+ seats and consistently opens them up for booking at T-24. But at T-24, GMs and FOs have free access to those seats, whereas if Delta were to open them up earlier, some of those same GMs and FOs might choose to pay for those seats.