Join Date: Apr 2009
Location: Bye Delta
Programs: AA EXP, UA Silver, HH Diamond, IHG Plat, Hyatt Plat, Marriott Titanium, Nat'l EE, Avis PC, Hertz PC
Posts: 16,630
Upgrades begin clearing at 5:00 PM Eastern time at 6, 4, and 2 days before departure for DM/PM, GM, and FO, respectively. The sweep can take several hours to run. Also note the time you receive the "You've been upgraded" email is not the time you actually clear, but minutes to hours later.
This all assumes there is V inventory at the window. If not, upgrades will not clear, of course.