A close relation of mine is on a Delta flight about 7 months into the future: DL643 on 11/29.

Now, this flight had its inventory zeroed out a few days ago. Typically, when this "schedule change Saturday" situation happens, I just say, okay, Delta's either going to do a schedule change with a new flight number, or reduce the frequency on this route and rebook my family member on another flight. Fine. We'll get a rebooking notice in the near future.

But several days have passed, and nothing has happened. The flight still shows up as operating, with zero inventory. We have not received any notification from Delta. I've checked in with three employees at two call centers and over chat (partly out of curiosity) and none of them can tell me anything more than what I just laid out. They can provide no information as to what the scheduling or inventory people are intending to do here.

Is Delta planning to eventually replace this flight with some other flight, but just hasn't figured out the aircraft availability yet (or how many staff they have who are trained on the type)? What is the point of stopping to sell the original flight if it will be replaced? Or perhaps it will indeed be canceled? But why the delay then? I refuse to believe that the flight is full five months in advance, so there must be some other reason why the inventory got zeroed out. Perhaps not selling this flight until they know they can recommit to operating it and follow through?

I've got a million miles under my belt and fly DL a ton (although no status with DL because I usually fly with my KE lifetime status). I've never seen a bizarre set of conditions like this. Any thoughts?

Edit: This flight in general used to be scheduled daily for the Thanksgiving holiday season (as part of a 2x daily frequency), but now it is showing up as zeroed out for most of the fall before resuming only 1x per week in mid-Nov and daily during Christmas holidays. This means DL is only selling one flight per day on this route through most of the Thanksgiving holidays, which seems rather odd given DL's significant presence at JFK and the 2~4x per day CUN-NYC frequencies operated by AA, UA, and B6 during the same period.

There is another direct flight that day, so in the case of a cancellation I presume I can just ask them to reaccommodate the passenger on that flight instead (less ideal schedule, but we'll live with it, no big deal). I am mostly posting this to see if anyone understands the situation better than I do, since I'm curious and want to learn more about this peculiar situation for future reference.