WSJ.com - How to Buy a Cheap Seat in First Class:
"Q-up, Y-up and Z fares aren't hard to find or buy, requiring just a few extra clicks of a computer mouse. Online travel Web sites such as FareCompare, Expedia Inc.'s Expedia.com, Sabre Holdings Corp.'s Travelocity and Cendant Corp.'s Orbitz let users search by specific fare type. While known as Q-up or Y-up fares, the codes airlines use to identify them sometimes contain additional airline-specific characters, as in one recent Delta fare labeled QUPBV.
At FareCompare, for example, bargain hunters can click 'Trip Search,' then enter the desired route and 'business/first class.' Using Expedia, select 'Additional Options' and then check the box to search for seats in business class or first class. Both sites search for the lowest fare in the chosen seating cabin. If a discounted first-class seat is available, 'QUP' or 'YUP' will pop up in the fare-class box shown by FareCompare. Otherwise, regular first-class codes such as 'F,' 'A' and 'P' will appear on the screen.
Expedia's Q-up fares can be seen by clicking on 'Rules and Restrictions.'"