Y-Ups accumulate bonus frequent flier miles; sometimes twice as many as coach airfare.
Most Y-Ups don't have advance purchase requirements.
Because most online airfare shoppers don't normally look for first-class travel, most airline ticket Web sites are going to make you dig to find a Y-Up.
If you use a travel agent, ask the agent to specifically search for "Y-Up" or "discounted first-class" airfares. When shopping online yourself, seek out a first-class search option, which is often buried under terms such as advanced search or other options.
Most Web sites don't show first-class quotes side-by-side with coach tickets. But there are new a few airline sites that are providing such searches. For instance, my site FareCompare.com has a tool that tracks more than 100,000 of these airfares from your favorite departure city.
Tell your travel agent to look for a seat booked in the "F," "A" or "P" cabin — these are the three domestic airline inventory codes where Y-Ups are booked. All domestic airlines book Y-Ups in one of these three codes.
Y-Ups are not for everyone, but for many they can make a huge difference in your air travel experience. Take care to follow these Y-Up rules of the road.
Y-Ups are not upgrades to an already purchased coach ticket.
If you miss a flight, ask the ticket agent at the airport to see if a Y-Up is available; it is many times cheaper than the walk-up coach price they will charge you to rebook your ticket.
Last minute and emergency travelers should always check for Y-Ups.
Although Y-Ups are mostly business traveler oriented, leisure travelers should check them for special occasions such as honeymoons or anniversary trips.
Caution: An airline may sell you a Y-Up even if a flight doesn't have a first-class cabin; check before you buy your ticket that the plane has a first-class cabin.
So, now you know what used to be the airlines' best-kept secret. What are you waiting for? Go join those smiling faces in the front cabin.
This work is the opinion of the columnist and in no way reflects the opinion of ABC News.
Rick Seaney is one of the country's leading experts on airfare, giving interviews and analysis to news organizations including ABC News, The New York Times, The Wall Street Journal, Reuters, The Associated Press and Bloomberg. His Web site FareCompare.com offers consumers free, new generation, software combined with expert insider tips to find the best airline ticket deal.