I mean, besides the welcome-bonus miles. (You knew that was going to be first!)

It’s not free checked bags, which is the benefit they advertise the most. (I never check bags flying domestic, and they already give you free checked bags on international flights, so it’s a wasted benefit to me.)

It’s the increased saver-award availability.

When you hold a United MileagePlus credit card and search for award availability on the United calendar, your cardholder status means you get to see more saver availability than someone who doesn’t have a MileagePlus card. So you have better odds of finding a great award redemption than someone who doesn’t have a United credit card. (And United award redemptions can be great because United doesn’t charge the substantial extra fees and surcharges that some other airlines do. Say I had an option of flying United to London for 40k miles or flying British Airways to London for 30k miles. I’d fly United in a heartbeat because the fees British Airways charges are going to be high. Example: I just did a sample search and the taxes/fees on one economy one-way flight from SEA-LHR were $231.20. But United? They have to charge the standard $5.60 security fee because that’s the law, but that’s it.)

Here’s an example of what that extra saver availability looks like: the dark blue box explains the “special member pricing” notation under certain award-search results you’ll see if you’re a cardholder.

Here are two examples to illustrate what kind of difference that can make. I’m a cardholder, so if I want to see what a noncardholder sees, I just do an award search without signing into my MileagePlus account.

You can see that the dates in the green boxes have saver availability at the lowest price available for cardholders. This is the same level of availability that United elite frequent flyers get, and with the card, you don’t have to have any kind of special status. You just get more chances of booking the best-value award tickets.

Here’s another example.

Not quite as many special saver-award days available on that second example to Tokyo as there were on the second example to Honolulu, but it’s still better.

You may be wondering if it’s really worth paying an annual fee just to get this extra benefit. Sure, an annual fee is worth paying for for most cards the first year you have them because of the welcome bonus, but what about after that?

The really cool thing about United’s card options is that the two main go-to cards—the United Explorer card and the United Business card—both have the annual fee waived the first year. And—here’s the great part—there’s a no-annual-fee United card that’s also available as an option to downgrade to. So you could apply for one of these cards with the higher bonus offers, earn the 50,000 bonus United miles (personal card) or 75,000 bonus United miles (business card), and then after the first year, call Chase and ask to downgrade your card to a United Gateway card, which has no annual fee and a low welcome bonus (20,000 miles). That way, if you don’t want to pay the $99 annual fee after that first free year, you can still keep your special saver-award availability superpower by hanging onto a United card. (Even the Gateway card comes with the increased saver availability.) And because the Gateway card’s welcome bonus is pretty low, you’re not wasting much by downgrading. Downgrading the card instead of closing the account altogether is smart because it keeps the account open, which helps your credit score stay higher. (Closing cards is something you should try to avoid whenever possible so your credit score doesn’t take a hit.)

Because Chase Ultimate Rewards points transfer to United at a 1:1 ratio, you can keep flying on United award flights even without having to get more United-specific cards if you don’t want to. You don’t have to book your flight using your United card to pay the taxes/fees, either. You can use whatever card you want. (But if you do use a United card that comes with benefits such as free checked bags, you’ll want to make sure you do book your award flight with that card or the benefits won’t kick in).

Even if you don’t live in a United hub city, keep United in mind. For destinations where you’ll have to connect anyway, it can make a lot of sense to fly them because of the low fees and increased saver availability.