In order to book an upgradable fare on United you have to buy a ticket in fare class W or higher. Here are the fare classes above W.
V
Q
H
U
E
M
B
Y
Only airlines could convolute something so simple as the ordering of the alphabet.
Related
The U.S. immigration decline 2025 is the first drop in
The FT reports on the excess inventory in certain parts
It should come as no surprise that in-game product placement