Frequent flyers can earn sky-high rewards with this card.

Pentagon Federal Credit Union's Premium Travel Rewards American Express Card gives you 5 points for every $1 spent on airfare. You'll receive 1 point per dollar for all other expenses.

If you spend $2,500 in the first 3 months -- easy to do with just a couple trips abroad -- you'll earn 20,000 bonus points that can be redeemed for flights, hotel stays, gift cards and more.

Charge more than $15,000 on the card in a single year and you'll get 2 complimentary lounge club visits, good at airports around the world, Gonzalez notes.

And unlike some other rewards cards, there's no cap on how many points you can earn or redeem.

To get the card, though, you must be a member of the PenFed Credit Union. You're automatically eligible to join the credit union if you or a relative are a veteran, in the military or have a government job. The same is true for members and employees of organizations like the Red Cross. Otherwise, you'll have to make a $15 one-time donation to join. Aside from that, there's no annual fee.