Elite UGs would come first and even though it's a small sampling (below) it shows Elite UG success isn't even all that sure:
Originally Posted by www.upgradesuccess.com
AIRLINE/ELITE STATUS/ENTERED/UPGRADED/upGrade Success!
NW/WorldPerks Platinum Elite/4/4/100.0%
NW/Gold/2/0/0.0%
NW/Silver/2/1/50.0%
TOTALS 8/5
making my answer the same as
Phil2016's. It might be possible for low elite travel periods, but otherwise not likely.