How airline miles work: a beginner's guide

Airline miles are a loyalty currency. You earn them by flying and by spending with an airline's partners, then you trade them for flights, upgrades and other rewards. The catch is that every airline controls its own currency, so the value of a mile depends on the program and how you use it.

How airline miles work, in one minute

Every major airline runs a frequent flyer program. When you join (it's free), you get an account number. Add it to every booking and every partner purchase, and miles land in your account.

Later, you spend those miles on an award ticket. Instead of paying the full fare in cash, you pay miles plus taxes and fees. Some programs also let you use miles for seat upgrades, hotel stays or other perks, but flights are usually where the value is.

Ways to earn miles

Flying is the obvious way, but for most people it isn't the main one.

• Flying: many programs now award miles based on the fare you pay, not the distance flown.
• Partner airlines: flights on partner carriers, including alliance members, can earn miles in your chosen program.
• Shopping portals: start an online purchase from your airline's shopping portal and earn miles per dollar at participating stores.
• Dining programs: register a payment method once, then earn miles when you eat at participating restaurants.
• Hotels and car rentals: many hotel and car rental companies let you earn airline miles instead of their own points.
• Promotions: airlines regularly run bonus offers, from double miles on certain routes to bonuses for trying a new partner.

What are miles worth?

There's no fixed answer. A mile is worth whatever you can get for it. Use the same 30,000 miles for a cheap domestic flight and you might get poor value; use them on a flight that costs a lot in cash and you could get far more.

A simple way to judge any award is cents per mile: subtract the taxes and fees from the cash price, divide by the miles, and multiply by 100. Our award value calculator does the math for you.

How to redeem miles well

1. Be flexible. Award seats are limited. Shifting your dates by a day or two can make a big difference.
2. Look at partners. Your miles often work on partner airlines too, which opens up more routes and more seats. See how airline alliances work.
3. Book early or late. Many airlines release award seats far in advance, and sometimes release more close to departure.
4. Watch the fees. Some awards carry high surcharges. A "cheap" award isn't cheap if the fees are close to the cash fare.

Common beginner mistakes

• Spreading miles across too many programs. Small balances in five programs are less useful than one meaningful balance.
• Letting miles expire. Some programs expire miles after a period of inactivity. Any earning activity usually resets the clock.
• Saving forever. Programs can raise award prices at any time. Miles are for spending, not hoarding.

Bottom line

Join the program of the airline you fly most, add your number to every booking, and earn through partners you already use. Then spend your miles on flights that would cost a lot in cash. That's the whole game, and it gets easier with every award you book.