United provides Global Premier Upgrades (GPU) to frequent fliers that can be used to upgrade one leg of a flight by one class, e.g., economy to business. However, for international flights, the economy ticket also has to be in minimum fare class ("W" typically), which is often significantly more expensive then the cheapest available ticket at time of booking. It's typically around $200-$300 more per leg. Other than being eligible for an upgrade, the higher fare class has no other benefits. That was actually confirmed to me by an United agent on the phone.
The upgrade is also dependent on availability of a special type of tickets (R-space). Availability at time of booking is quite rare on most routes. You can still apply the GPU, but you get wait listed. If R-space becomes available or United doesn't sell all business class seats for cash, they will upgrade by going down the wait list. Often the upgrade does not go through. In this case, the GPU is returned to the customer. However the price difference of the tickets is not. So you have spent $200-$300 for nothing.
So in short: at time of booking, you need to decide whether you want to spent extra money for a chance at an upgrade. If you get it, great. If not, the money is gone with no value or benefit and United keeps the cash. Some frequent flier web sites refer to this actually as the "upgrade lottery".
- You wager money
- there is an event with uncertain outcome
- if the the outcome is "good" you have a substantial gain, if the outcome is "bad", you lost your money without any benefit from it. It's a simple "yes"/"no"
- You have little or no information to predict the outcome at time of wager.
- You have no control on the outcome