Delta's award pricing (what a flight costs in miles) is dynamic, which is airline speak for "it depends." There's no published award chart, so the same seat can cost wildly different amounts of miles from one day to the next.

That unpredictability is why some frequent flyers jokingly call SkyMiles "SkyPesos." It's also what makes room for some of the cheapest award flights out there, because nothing stops Delta from slashing prices, either. The fix is learning to be a little dynamic yourself.

Delta SkyMiles is Delta's free loyalty program, which lets you earn miles and redeem them, mostly for flights.

Sign up on delta.com before you need it, since you'll need a SkyMiles number to transfer points or earn miles on a flight. Members also get free Wi-Fi on most Delta flights.

SkyMiles don't expire, which is a big deal if you only fly Delta once in a blue moon. Most points experts value them at a little over a penny each.

To see whether a redemption is a good deal, use this quick math:

(Cash price − taxes and fees) ÷ miles required = value per mile

Say a flight costs $300 in cash or 25,000 miles plus $6 in taxes. That's ($300 − $6) ÷ 25,000 = $0.012, or about 1.2 cents per mile, which is a solid deal.

Delta is a founding member of SkyTeam, one of the world's three big airline alliances. Think of an alliance as a family. Members share frequent-flyer perks, so you can earn and redeem SkyMiles on carriers like Air France, KLM, Korean Air, Virgin Atlantic, and Aeromexico.

Delta also has a few "cousins" outside SkyTeam, including LATAM and WestJet, where you can still earn and redeem SkyMiles.

Most partner flights show up right alongside Delta's own when you search award flights on delta.com. Just know that a few partners can only be booked by calling Delta.

On flights sold by Delta (the flight number starts with "DL"), you earn miles based on what you pay, not how far you fly. General members can earn 5x miles per dollar on the base fare and airline-imposed fees, and Medallion members can earn up to 11x depending on their tier. Taxes don't count, and basic economy fares (Delta Main Basic) don't earn miles at all, while other basic fares earn at a reduced rate.

Partner flights work differently. If you book directly with a partner airline and add your SkyMiles number, you'll typically earn based on distance and fare class instead.

Delta even rewards you for waiting at baggage claim. If your checked bag takes more than 20 minutes to reach the carousel after an eligible domestic flight, you can claim 2,500 bonus miles. Just make sure your SkyMiles number is on the reservation and file your claim within two hours of arrival.

This is the move many beginners miss. American Express Membership Rewards® points transfer to SkyMiles at a 1:1 ratio, so 20,000 Amex points becomes 20,000 SkyMiles. Cards such as the American Express® Gold Card earn bonus points at restaurants and U.S. supermarkets, which can add up faster than a Delta card would on the same spending.

The real perk is flexibility. Keep your points with Amex until you've found a flight worth booking, and you're not locked into Delta if another airline transfer partner has a better deal (future you, staring at a great fare to Tokyo on another airline, will be grateful).

Just note that Amex adds a small fee to cover federal excise taxes when you send points to a U.S. airline like Delta. Marriott Bonvoy points transfer to Delta, too, but at a 3:1 ratio that's rarely worth it.

Delta has a lineup of credit cards issued by American Express, ranging from a no-annual-fee option to premium cards with lots of perks. Everyday earning on these cards is modest.

The bigger draws are welcome bonuses, free checked bags, a 15% discount on Delta award flights, and, on higher tiers, extra help toward elite status.

That 15% discount, called TakeOff 15, is the sleeper perk, and it comes with every Delta card except the no-annual-fee one. Redeem 100,000 miles on Delta flights in a year, and you'd save 15,000 miles, which could be worth more than $150. If you book even a couple of award trips a year, this perk could help a card pay for itself.

You can also earn miles on everyday spending:

These miles stack on top of whatever your credit card earns. Buying miles from Delta, on the other hand, is almost never a good deal.

Booking is the easy part. On delta.com, toggle "Shop with Miles," then open the price calendar to see several weeks of award prices at once.

Log in first so any cardholder discount shows up, and check the box to include nearby airports in case a different airport is cheaper.

Before you book, know these rules:

Skip redeeming miles for gift cards, merchandise, or most paid upgrades, since they usually get you less value than a flight.

A sweet spot is a redemption that gets you outsized value compared with paying cash. With Delta, they mostly come down to timing and flexibility. Short domestic flights are a quiet standout, and with the cardholder discount, some can dip below 5,000 miles one-way.

Delta periodically slashes award prices without much warning. Travelers have spotted roundtrip economy to Europe below 20,000 miles, Hawaii in the low 20,000s, Delta One business class to Europe around 115,000 miles each way, and Delta One to Asia under 100,000.

Delta lists some deals on its award deals page, but the best ones often aren't advertised (rude, but fine).

Alert services can do the watching for you. Thrifty Traveler Premium flags SkyMiles flash sales as they pop up (use code DEPARTUREDIGEST for $20 off your first year).

Award prices out of Delta's hubs, such as Atlanta, Detroit, Minneapolis-St. Paul, and Salt Lake City, are often higher, since Delta knows travelers there have fewer alternatives. If you live near another airport, run the same search from there, even if it means a connection.

This one feels backward, but it works. Air France-KLM Flying Blue and Virgin Atlantic Flying Club, both SkyTeam partners, often charge fewer miles than Delta does for the exact same Delta flights. Flying Blue is especially good for Delta One business class to Europe. Just compare the total cost, not only the miles, since taxes and fees can differ and these award seats can be hard to find.

That matters because standard Delta One awards can climb past 300,000 SkyMiles each way. Flying Blue miles and Virgin Points transfer from programs including Amex, Capital One Miles, Chase Ultimate Rewards®, Citi ThankYou® Rewards, Bilt Rewards, and Rove Miles, so you don't need to fly these airlines to collect them.

You don't need elite status to get good value from SkyMiles. Still, it's worth knowing how it works if Delta ends up being your go-to airline.

Delta's elite program is called Medallion, and it has four published tiers (yes, there’s an invite-only Delta 360 tier for VVIPs). You qualify by earning Medallion Qualification Dollars (MQDs), which is Delta's way of tracking how much you spend with the airline.

You earn 1 MQD per dollar on Delta-sold flights (excluding taxes) and Delta Vacations packages. Premium Delta cards can add more through card spending and an annual head start. Here's what each tier requires in a calendar year:

Once you qualify, your status is good for the rest of that year, all of the next, and through Jan. 31 of the year after. All Medallion members are eligible for complimentary upgrades, free preferred seats, waived checked bag fees, and priority boarding.

Gold and above also get SkyTeam Elite Plus, which includes lounge access on international SkyTeam trips. Platinum and Diamond members pick from Choice Benefits like bonus miles, travel vouchers, and upgrade certificates.

Medallion status alone won't get you into Delta Sky Club lounges on domestic trips. A premium card like the American Express Platinum Card® is usually the easier route, with a limited number of Sky Club visits each year when you're flying Delta, plus access to Amex's own Centurion Lounges.

Delta SkyMiles is worth joining for just about everyone, even if you rarely fly Delta. It's easy to join, your miles never expire, and even occasional flyers get perks like free Wi-Fi onboard.

Actively collecting SkyMiles makes the most sense if you fly Delta regularly, already earn Amex points, or can bend your dates and destinations to catch a sale. If you're new to points, booking one inexpensive domestic award is a great first win.

SkyMiles are a tougher sell if your dates are locked and you're hoping to fly Delta One at the standard price. In that case, a more flexible currency or the Flying Blue or Flying Club workarounds will usually go further.

Whether you're sitting on 6,000 miles from a few work trips or 100,000 from a welcome bonus, the strategy is the same. Delta's pricing is dynamic, so the best deals go to travelers who stay flexible on dates, airports, and destinations.