Flying has a learning curve. Though breezing through an airline-booking website just to go about your day seems tempting, doing so can cause some headaches. Unlike a movie theater where every seat has a static price, airline seating feels more like a hard science. By the end of this blog, you may wonder why they don’t teach college classes on the subject.

Ever wonder why you can’t sit next to a friend or a spouse, or why your ticket isn’t refundable? Simply put, airlines use fare classes to control inventory and maximize profits. These fares translate into codes that you can see on you ticket. These codes define every aspect of your flight from prices to restrictions and rewards.

Look at it this way. Airlines divide their planes into sections then into seats. Terms like First Class, Business Class, and Coach surely sound familiar. Each seat within a section has a unique set of bonuses and restrictions that affect its price. One seat in coach may have great discounts while another offers bonuses on an airline programs frequent flyer miles.

Each airline uses different codes though some appear largely universal. For example:

Y = Full Fare Economy

J = Full Fare Business

F = Full fare First-Class

When you book a seat in the economy class, look at the airlines inventory. You’ll commonly see something like F6 or Y12 – this indicates how many seats in that section fall under this category. In this example, six seats are available for first class. The thing is, more than just these letters exist. Check any airline site, you’ll see loads of codes for economy classes (more than just Y anyways).

Delta alone has a huge variety of fare codes depending on how and where you want to fly. You can see a more detailed list here:

Let’s say you see a Y and a Q economy seat. A “Y” seat is more expensive than “Q” seat. Both are in coach, but if you see Q0 / Y5, you’re stuck with “Y” despite its price.

This is because of the benefits and restrictions that apply to them. They affect the price. Essentially, this is why you’ll see prices rise and fall each day you check an airlines website.

Things like frequent flyer miles, reserved seats, and pecking order for upgrades (if an upgrade is available to your seat at all) affect prices. Remember that Y seat that was more expensive? It might be because they offer miles or place you sooner in the line for upgrades. Don’t want either of those perks? Well unfortunately, it’s all they have left. This is why you may find yourself paying more than the fellow next to you who happens to have that cheaper Q seat.

The cheaper the seat though, the more restrictions are placed on it. Let’s say you found a cheap economy seat, but now you have a family emergency and can’t make the flight. Did you check your fare class when you booked? It might say that your cheap seat is non-refundable, so now you’re stuck with the bill.

Another scenario: You and a friend are traveling. You booked online and found a cheaper rate than your friend. Great, but this also means you might be sitting on opposite sides of the plane. The airline regulates those cheap seats to a few rows in the back. Your friend, who paid for a full fare seat, must sit in the front.

Airlines offer a chance to alleviate seating problems through seat assignments. For an extra charge, you can secure a seat within the same fare class (you can’t assign yourself a seat in First Class if you booked Economy for obvious reasons). But even this isn’t perfectly airline proof. Airlines reserve the right to reassign when necessary for any reason ranging from equipment changes (i.e. a 737 vs. 757) to accommodating that person with the window seat who needs the aisle because they get sick. Most airlines do all they can to move willing passengers to different seats in order to accommodate families, but like most airline policies, it isn’t guaranteed.

The problem with learning about fare basis codes is that you really can’t use to them to “game” the system.  A little bit of preplanning helps though. Know the seat you’re paying for with all the little idiosyncrasies that make up its identity. At least it should make the process a little more understandable and less painful.