I am on the verge of needing to buy a ticket with short notice from here to Denver, and the best times for flights are on United. (UAL). Checking prices the lowest restricted fare is $849 round trip, but the lowest first class fare is $900!
There are restrictions on the first class fair but it does provide some flexibiity to change without penalty, etc.
And of course, as jerrycoin might note, the FC Cabin is a licensed "pharmacy," dispensing "medications" in great amounts for the 2.5 hour flight
If the "pharmacy" has a fare class of "P" which I'm guessing it does then it will cost you about $200 for change or cancellation. I believe the "Z" fare is fully changeable and refundable. Here is a way to test it, when you are looking at the very first reservation page where you put in your days of travel and such, scroll down to the fourth blue line across the screen and you'll see "What is your fare preference". Click on flexible and then continue to find out what the ticket price differences are, usually the higher price is no penalty tickets.
The other way is to go further into the booking process just before the credit card selection and there should be a spot just above the trip insurance and credit card information that tells you the ticket either has no penalty or it's non-refundable and changes cost you $$. The non-refundable simply means you don't get your money back it is saved and able to be applied to another ticket within a year and when you decide to use the $$ for a ticket that's when the change fee gets applied.
One fare (the lowest) was Z and another was A class, Both have "issues"
My handy decoder chart (shown here) is good to check.