When you make purchases with your credit card, you earn points or miles that can be redeemed for free flights and for many other travel-related expenses. Often, travel spending on airlines, rental cars and hotels earns bonus points. Some airline credit cards even allow for higher point valuations when points are redeemed for airline rewards.

Most airline credit cards earn at least two points or miles per dollar on airline purchases.

Many airline credit cards earn rewards that you can redeem as cash back, travel bookings or transfers to travel partners. Some airline cards have rewards you can redeem with multiple partners, such as within an airline alliance.

Sign-up bonuses worth at least $100 are common, and many cards offer sign-up bonuses worth $500 or more.

Most airline credit cards have an annual fee, but a few waive the annual fee for the first year.

You can expect to have an annual percentage rate of at least 15% with airline cards, and many have a minimum APR between 15% and 18.99%.

In addition to earning free flights, many airline credit cards come with travel perks such as free checked baggage, priority boarding, seat upgrades, concierge services or access to members-only airport lounges.

Before you apply for an airline credit card, take a look at this checklist to see if these cards are a good fit for you.

1. You frequently fly with the airline or plan to do so in the future. If you don't travel frequently or visit destinations served by a particular airline, a general travel rewards card may be a better choice than an airline credit card.
2. You have good or excellent credit. Airline credit cards usually require good to excellent credit. You should have a FICO credit score of at least 670 before you apply for an airline rewards credit card.
3. You can pay off your balance each month. You should be debt-free and avoid carrying a balance on your airline rewards credit card, as interest charges can quickly wipe out any rewards you earn.

Airline loyalty, spending habits and preferences are different for every traveler, so the "best airline credit card" will differ from person to person.

When you're trying to pick the best airline credit card, follow these six simple steps to evaluate each card:

1. Pick the right rewards program for you.

Co-branded airline credit cards sometimes offer the biggest benefits toward airfare and related purchases. Travel rewards cards provide broader rewards categories, but many don't offer the same level of rewards for airline-based earnings.

Co-branded cards: Airline credit cards are often called "co-branded cards" because they are tied to a particular airline, such as Delta or United, which can limit your travel options.

If you're signing up for a co-branded airline card, consider airlines with hubs at your local airport. For example, many frequent flyers in Atlanta fly with Delta because the airline has a huge hub there.

Travel rewards cards: With travel rewards cards, points or miles can be used for flights, hotels and rental cars without being restricted to a particular airline or an airline partner. They can also be redeemed for merchandise or cash back.

Take your time and decide which type of rewards will benefit you the most. The best type of credit card is the one that works best for you.

2. Calculate earning potential.

With the best rewards on airfare and related purchases made directly with the airline, co-branded airline cards promote brand loyalty.

General travel rewards credit cards often provide you with more chances to earn a higher rewards rate. They may offer broader bonus spending categories or simply earn a higher rate on all purchases.

3. Calculate sign-up bonuses and welcome offers.

Sign-up bonuses and welcome offers provide a lot of points or miles, but only after you meet certain spending requirements.

But a warning: Don't get dazzled by a fabulous sign-up bonus. Make sure the credit card is right for you, apart from the sign-up bonus. In other words, keep a cool head and choose wisely.

4. Calculate redemption value.

For most travel rewards cards, one point is equal to 1 cent. Co-branded airline cards may offer from 1 cent to 5 cents per point, depending on the flight, but it's difficult to put a consistent value on what you earn in rewards because it's always changing based on flight prices, route, availability and more.

While some airlines have a published award chart you can use to estimate value, others don't.

Understanding how an airline card's point system works is an important part of selecting a credit card. According to U.S. News research, points earned with the Delta SkyMiles Gold American Express Card are worth an average of 1.21 cents.

5. Subtract annual fees.

Subtract annual fees from your potential earnings to estimate the true rewards value of a card. Although a card may have annual fees, the benefits and rewards could offset those costs.

6. Understand travel benefits.

Airline rewards cards come with benefits that can be helpful for traveling and making purchases. Many travel cards offer perks, including no foreign transaction fees, trip cancellation or interruption insurance, auto rental insurance and lost baggage protection.

Airline co-branded cards typically provide more valuable cardholder benefits than general travel cards. They may offer benefits directly with the airline, which could include free checked bags, priority check-in, priority boarding, companion tickets and access to airport lounges.

Make sure the fees are worth it. Consider your plans for using the card, earning rewards and taking advantage of benefits. If you won't use it enough to offset associated fees, the card may not be worth it.

Combine cards. If you have a general travel rewards card but often fly one airline, it may make sense to supplement with an airline credit card. Your general travel rewards card may offer better rewards on bonus categories, but your airline card will earn the most when you fly with that specific airline.

Maximize loyalty tier rewards. To do this, you have to travel as much as you can with a single airline. Keep close track of your qualifying purchases, points and flights, and find out when qualifications expire. Schedule your trips so that you can maximize earnings within the calendar year and earn a tier upgrade. You'll need to think ahead to make it work out.

Maximize bonus category returns. Understand the criteria for earning bonuses, and keep track of any promotional programs your credit card company offers. Keep in mind that bonus spending with airlines may not be limited to flights. And don't overspend to get the bonus or the rewards. Have a budget for your airline credit card and stick to it.

• You can use points for travel: Rewards can be a major incentive for frequent travelers. Airline credit cards may offer bonus points for purchases with the airline, for other travel-related purchases, or on categories such as dining, entertainment and groceries.
• Airfare discounts: Even when you're not redeeming rewards points or miles, you can use your airline card to save money.
• Airline privileges: Many airlines offer special privileges for airline credit card holders, including free checked bags, priority boarding, discounts on in-flight purchases and seat upgrades. Your card may also get you into private airport lounges with complimentary beverages, snacks, internet access and workspaces.
• Travel perks and protections: Many airline credit cards waive foreign transaction fees, which is important if you travel overseas. They may also offer insurance and protection for travelers, including trip cancellation insurance, car rental insurance, lost baggage protection and emergency assistance.

• Complicated rewards structure: With airline co-branded credit cards, point valuations are fluid. Determining just how much a point or a mile is worth can sometimes be a challenge.
• Annual fees: Many airline credit cards have annual fees, so you'll have to make sure your rewards will outweigh the cost.
• Higher purchase and balance transfer APRs: Purchase and balance transfer APRs for airline credit cards may be higher than other types of rewards cards.
• Credit score requirements: Airline credit cards are often reserved for consumers with at least good credit (FICO score of at least 670).
• Restrictions on earnings: Many airline credit cards only earn bonus points or miles on purchases with a specific airline. Or some bonus categories may only earn the bonus rewards rate on a limited amount of annual purchases.
• Restrictions on redemptions: Points or miles earned with an airline credit card may only be usable with a particular airline or with its partners. There may be blackout dates, which limit the flights you have access to as well as the dates when you can travel.

A good airline credit card is worth it as long as the rewards you earn outweigh the annual fee.

The majority of airline credit cards come with some sort of checked bag allowance, though they are usually airline-specific cards with perks that can only be used with that brand.

It is common for the card issuer to charge an annual fee, but not in every case.

That depends on the rewards program. For example, an airline-specific card may earn miles with the same value as miles earned from that airline’s frequent flyer program. With travel cards that earn points, the point value usually varies by redemption method; using the credit card issuer’s travel-booking platform may give you more value for your points than transferring them to an airline’s frequent flyer program.