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
Why AI in Cybercrime Demands Attention Artificial intelligence is no
The future of senior care is no longer limited to
Team trust is the lifeblood of any well-functioning team, but