At NerdWallet, we strive to help you make financial decisions with confidence. To do this, many or all of the products featured here are from our partners. However, this doesn’t influence our evaluations. Our opinions are our own.

For a limited time, Capital One is offering a bonus when you transfer miles to Flying Blue, the joint airline loyalty program of Air France and KLM Royal Dutch Airlines.

Travelers with one of the mile-earning Venture or Spark Miles cards can get a 20% bonus on transfers to Flying Blue, meaning 1,000 Capital One miles will get you 900 Flying Blue miles. The normal transfer rate is 2:1.5, meaning 1,000 Capital One miles would typically get you only 750 Flying Blue miles. This offer ends June 30, 2019.

» Learn more: Nine easy ways to earn airline miles

Who’s eligible for this offer?

If you carry a card that earns Capital One miles, you're eligible to take advantage of the bonus offer. Those cards are:

You'll also need to connect your Flying Blue account to your Capital One account to be able to transfer the miles.

Why transfer points?

Capital One added the ability to transfer miles to airline loyalty programs in December 2018, following in the footsteps of travel rewards programs like American Express Membership Rewards and Chase Ultimate Rewards®. That's in addition to the ability to redeem Capital One points for a credit on your statement against any travel purchase, at the rate of 1 cent per point.

If your goal is to redeem miles for business or first-class travel, transferring Capital One miles to Flying Blue can be much cheaper than "erasing" the cash price of a ticket with your miles. For example, let’s say you want to book a one-way business class ticket from San Francisco to Amsterdam this July. The cheapest award option through Flying Blue when we last checked was 63,000 miles. Assuming the regular 2:1.5 transfer ratio between Capital One and Flying Blue, that would translate to 84,000 Capital One miles — plus about $230 in taxes and fees.

In comparison, paying cash for the same routing in July could cost anywhere from around $1,600 with stops to upwards of $9,000 for a nonstop. That would require a minimum of roughly 160,000 Capital One miles to erase the full cost of the ticket — or over 900,000 miles.

» Learn more: Travel rewards bucket list: Showering on a plane

If you can find award availability with Air France or KLM that works with your schedule, transferring miles can be smart. Check out the Flying Blue Promo Rewards list for even deeper potential discounts.

How to Maximize Your Rewards

You want a travel credit card that prioritizes what’s important to you. Here are our picks for the best travel credit cards of 2020, including those best for:

Planning a trip? Check out these articles for more inspiration and advice: Find the best travel credit card for you How to get started with frequent flyer programs This strategy is how I started earning major travel rewards