I have a friend who was flying IAD-LAS on a paid F ticket. My friend has no status and does not have the credit card. His IAD-LAS flight cancelled and he was rebooked onto IAD-DEN-LAS but they rebooked him in economy despite having a paid F ticket, and there were F seats open on IAD-DEN with no one (left) on the upgrade list. When he was rebooked, the upgrade list was already cleared on IAD-DEN, and my friend was put on the upgrade list. Since he was a displaced F passenger, he was #1 on the list and ended up clearing. Is there a reason why United couldn't just confirm him in F?