I'm curious about how frequently and when the flight alerts are triggered. Is it only once per 24 hours, or more frequently? I had originally assumed it was nearly real-time, but had the following experience yesterday:

I set up an alert to advise me when DL G upgrade inventory (at least 1 seat) would be available for a specific flight about a week ago as it was G0 at the time.

Yesterday, I phoned DL to book a round-trip itinerary with SWUs. The itinerary has six legs (3 each direction) and only four of the six had upgrade inventory available at time of booking, so those four legs were confirmed and I was waitlisted by DL for the other two. I had EF open while booking and one domestic leg was definitely showing G0 around 7.30 pm my time while on the phone with DL, and the agent also confirmed no availability.

Being a bit obsessive, I checked EF at 10.30 pm (about 3 hours later) and it suddenly showed G3 available, so I quickly called DL and they were able to confirm the upgrade (for two pax). After doing so, EF showed G1.

I had not received an alert about this availability, and only at 5.16 am this morning did I get the EF alert. When I checked EF, it was already back to G0. So I would have missed the upgrade if I had not checked manually and had relied on the alert.

So I wondered how often email alerts are toggled and sent - if only once per 24 hours, I would imagine one could miss availability.

Susan