UA upgrade from Econ to Business
 

Read somewhere on another forum a few years back that you could purchase an upgrade to Business from Economy for $US500 to LAX/SFO with UA on the day you travel when you check in. Does anybody know whether this happens? Cheers:)

This is called an on Departure Upgrade. Usually cost around USD 550-750 one way. It is ONLY available at check in if there is any Business class seats around. I have not flown the new Business Class, so I am unsure this policy has changed. Better try read FlyerTalk forum

Sam