Delta FO here.

I book fares through my corporate engine, so I don't have a lot of flexibility with fare class, as the engine gives us the cheapest (read: sLUT fares).

I downloaded the free 5-day trial of Expert Flyer tonight and noticed there's "V" availability on one of the legs of my next flight. What does that mean? I already booked a seat in Q. I assume "V" is a fare class like any other, and has to be selected at the time of booking? The description said "domestic complimentary upgrades" or something of that sort.

Can someone in plain English (for a not-so-seasoned flyer) tell me what it means?