First up is the Gold Delta SkyMiles Card from American Express.

Welcome bonus: Earn 30,000 Delta miles after you make $1,000 in Delta purchases in the first three months. Plus, receive a $50 statement credit when you make a Delta purchase in the first three months.

Annual fee: $0 introductory annual fee for the first year, then $95

Earning miles: 2 miles per dollar spent on Delta purchases, and 1 mile per dollar on everything else

Top benefits: Free checked bag on Delta flights, priority boarding, 20% off in-flight purchases, no foreign transaction fees

In addition to the welcome offer, the Gold Delta Amex card comes with a handful of incredibly useful — and valuable — perks.

If you have the card open, you get a free checked bag on Delta flights, as does each other person on your reservation. Delta normally charges $30 for the first checked bag on each flight — so $60 for a round-trip — meaning that for a family of four, the free checked bag benefit could save $240.

The card also offers priority boarding to everyone on the cardholder's reservation. If you aren't checking a bag, that can come in useful — by boarding a little earlier, you'll get better access to the overhead compartments and won't have to worry about space running out.

Other benefits include a 20% discount on in-flight purchases (in the form of a statement credit), such as food or drinks, and no foreign transaction fees.

While the Gold Delta card is a great option, you may also want to consider the Platinum version (the Platinum Delta SkyMiles® Credit Card from American Express). Although it has a higher annual fee —$195, not waived the first year — it offers a companion pass each year on your cardmember anniversary. You can learn more about the companion pass benefit and the Platinum SkyMiles card here.

Note that starting in 2020, Delta credit cards will be updated with new benefits including additional 2x bonus categories for earning miles (US supermarkets and restaurants) and a $100 Delta flight credit after you spend $10,000 on the card in a year. The Gold Delta Amex annual fee will also be increasing to $99.

Click here to learn more about the Gold Delta SkyMiles card.