Think all first class tickets are the same? Think again.

When you fork over the cash for a first-class ticket, you expect to actually fly first class, right? Well, unfortunately for some fliers, that's not always the way it works out. That's why it can pay to understand the pricing anomalies of how airlines arrive at their fares.

Without getting into the nitty gritty of revenue management systems, airlines have many different ticket prices for every city pair. Each ticket price for any particular route is assigned a specific letter, and that letter comes with different rules for changes, cancelations and routing restrictions.

One fare, typically known as a Y-UP, is a favorite of penny-pinching business fliers, especially those whose companies stipulate that they cannot purchase first-class tickets. The letter Y is the standard airline code for an economy ticket, and Y fares are typically the highest-priced – but most flexible – of all economy class tickets. Since most economy seats are more or less the same, most people wouldn't choose to pay for a full Y fare unless they were purchasing one of the last seats on the plane or needed the flexibility. Instead, most people get stuck with the Y fare.

To encourage people to buy the full-fare economy class ticket, many airlines offer what they call Y-UP tickets, which provide a complimentary upgrade to first class at the time of booking. The problem with the Y-UP is that it appears as a “first class” ticket on most airline websites, despite technically being an economy ticket. Most passengers don't even know they've purchased this particular fare class until there’s a flight cancelation, or their flight becomes overbooked and they're downgraded in favor of someone who actually paid for the more expensive fare.

Do you have any rights in this situation? Points guru Gary Leff of View from the Wing advises fliers to seek assistance from another agent (perhaps on the phone instead of at the airport) if not given the option to rebook into first class. Members of the frequent flier forum Flyertalk have shared mixed experiences; some were rebooked into first class after a flight cancelation, while others had to settle for riding in the back of the plane. It all comes down to how many seats are left to assign – and the number of displaced passengers that paid for a first class fare have priority.

American Airlines spokesperson Joshua Freed said that if there is space, the airline would re-accommodate a Y-UP type fare in first class. But the nature of irregular operations (delayed or canceled flights) means that sometimes there are no first class seats left, so it is possible for that passenger to be downgraded (although they technically had an economy ticket with a possible upgrade to begin with). If that occurs, a difference in the cost of the fare may be refunded to the flier.

Y-UPs are not supposed to be a bargain for economy class fliers, but they are a bargain for those that like to buy first class or who typically buy tickets at the last minute. What is great about them is that depending on the carrier, they often have more flexible change or cancelation policies than regular economy fares.

So how do you know if you’re buying a Y-UP? Well, if you see a first class ticket that is cheaper than an economy class seat, there’s a good chance that’s a Y-UP fare. Rahsaan Johnson, a spokesperson for United Airlines, told Road Warrior Voices:

"While it’s feasible that a market pair could have a discounted premium fare that’s lower than the highest economy fare, the system is programmed to offer the lowest fare."

That fare could often be in first class, so don't assume that coach is always going to be the cheapest, especially as the date of travel approaches.Some airlines do allow you to click on the fare rules on the website, which may say that it is a Y-UP ticket. You can always ask an airline reservations agent to specifically search for these fares for you, and it can often pay off to be on the look out for these kinds of tickets.