Join Date: May 1998
Location: Reno, NV (RNO)
Programs: AA LT Platinum, AS, UA Premier Silver, DL, HHonors Gold, Marriott LT Titanium, Hyatt, IHG Platinum
Posts: 4,723
I believe US allows companion upgrades even if you are not traveling under the same PNR. AA may allow this also, although I am certain that UA does not.