By Adam Jusko, ProudMoney.com, adam@proudmoney.com

Sometimes trends are hard to spot, other times they hit you over the head. Today it’s the latter, as both United Airlines AND Delta Airlines announced new credit cards that don’t require an annual fee. In both cases, the airlines are giving more options to those who don’t travel enough to pay for a perks-laden airline card but who would still like to earn travel rewards on all their purchases.

United’s new credit card entry, issued in partnership with Chase, is the United TravelBank Card, which offers 2% earnings in “TravelBank Cash” on United purchases, and 1.5% on all other purchases. You’ll notice that these are not MileagePlus miles. Instead, “TravelBank Cash” goes into your United account and can be used like cash to offset or completely pay for United travel. In this way, the card is really more like a number of general travel rewards cards on the market currently, except for the fact that your rewards are actually limited to this one airline. While you do get some other perks, like 25% off your United in-flight purchases and no foreign transaction fees, you have less flexibility to use the rewards you’ve earned.

Delta’s new entry is more of a traditional airline frequent flyer card in that you do earn Delta SkyMiles with every purchase. The Blue Delta SkyMiles Credit Card is an American Express card that gives you 2 SkyMiles per dollar on restaurant purchases and on Delta purchases, and 1 SkyMile per dollar on all other purchases. The 2 SkyMiles per dollar on restaurant purchases is unique to this card, so it is actually a place where the no-annual-fee card is better than the Delta cards with annual fees. However, the Blue Delta SkyMiles card does not offer certain perks that its paid, sister cards do offer, such as “first bag checked free” and priority boarding.

For our (proud) money, Delta has the better card introduction here, in that it takes advantage of the airline’s current frequent flyer program while also spicing things up a bit with the 2-miles-per-dollar reward on restaurant purchases. The United Card, on the other hand, creates a new class of reward for United flights, which may cause confusion among new cardholders. While its reward formula compares favorably to other general-market travel cards and cash-back cards, the ability to use those earnings only on United purchases gives it less flexibility than those general-market cards.

Nevertheless, consumers love travel rewards and both of these cards give potential customers a new, no-annual-fee way to earn, which is likely to be good business for both these airlines and their card-issuing partners.