Several airlines, including United (UA) and American (AA), have begun offering a “Basic Economy” product that offers a lower fare, but higher restrictions. There a few things to be mindful of when considering the purchase of one of these low-cost fares.

Basic Economy fares typically do not follow the traditional “one carry-on bag plus one personal item” rule when traveling. In order to wrap your head around the peculiarities of these fares, it’s best to take a step back and consider the situation from the perspective of the airlines.

Overhead storage space has long been in short supply. How many times have you followed the rules regarding the size of carry-on baggage only to hear the gate agent announce: “We have a very full flight today, so passengers in later boarding groups may have to gate check their carry-on item?”

Basic Economy fares were born in an effort to prevent these situations from happening. These fares limit passengers to one item brought into the cabin. All other items must be checked for an additional fee prior to boarding; if a passenger forgets and has an item checked at the gate, there are additional “gate handling charges” or “gate service fees.” Essentially, if you hold a ticket in Basic Economy and you have to check a bag (whether at the ticket counter or the gate), you will incur a charge of some kind.

The over-arching goal of Basic Economy fares is to limit those passengers to bringing one item, no larger than a personal item (backpack, laptop bag, etc.), into the main cabin. When considering whether or not to purchase a Basic Economy fare, be sure to also research the checked bag fees for the airline you’ll be flying. Sometimes, a full fare economy ticket may wind up being cheaper in the long run than a Basic Economy ticket plus extra fees.