Originally Posted by findark

Just to be clear, I believe you are talking about change fees.

There is never a fee or charge to cancel a ticket, on any carrier, and there never has been. A carrier is always happy to remove your reservation on a flight and keep your money. After you cancel a ticket, all you have is a canceled ticket - then you presumably want to do something with it.

A "cancellation fee" usually refers to a fee for refunding a ticket once you have canceled it. This is an uncommon provision; most tickets are either non-refundable (cannot be refunded at all), or refundable for no fee. However, some international fares (historically to Asia and Australia) are refundable-minus-penalty or carry a cancellation fee.

A "change fee" is a fee to use the value of a canceled (or valid) ticket toward other travel.

Although United has announced a policy, all of these things are actually encoded in the fare rules. Right now, if you do not fly in Basic Economy, United has no change fees in any market that I am aware of (including international markets, but check the fare rules before you trust me). If you use United fares (which will happen if you buy a ticket from United), then all of your travel will be bound by these rules, regardless of which airline(s) you are scheduled to travel on.

I did check, and neither DEN-LIS nor DEN-OPO have change fees, and note that if your ticket originates in the US, you use the DEN-OPO fare to come home, not the OPO-DEN fare.