Citi ThankYou points accumulate quickly and can be spent flexibly, making it a convenient rewards program. Unfortunately, Citi keeps only one partner for points transfers -- the Hilton HHonors Program. But you can get United flights and even some Mileage Plus points through your Citi ThankYou rewards program. Just redeem your ThankYou Points for a United flight, using a Mileage Plus credit card to back up the transaction.

Sign into your Citi online account. Scroll to the bottom of the Rewards screen to see how many Citi ThankYou points you have accumulated. Click "View/Redeem" underneath the ThankYou points balance.

Click "Flights" on the left side of the screen, underneath the heading "Travel Center."

Fill out the flight search engine. Choose a round-trip, one-way or multi-destination flight. Enter your departing city, destination and dates of travel; and choose how many passengers. Click "Search" at the bottom of the menu.

Find United flights on the results page. Each flight will show the cost in Citi ThankYou Points, as well as the monetary price. Click the United flight that best suits your needs.

Click the "Air Reward" box under the Payment Options tab, then enter how many ThankYou points you would like to put toward the cost of the flight. You can pay for the entire flight with points; or you can cover some of the cost with points, and pay the rest with a credit or debit card on the next page. Click "Add to Cart."

Pay for the balance of the flight with a credit or debit card. Use a Mileage Plus credit card to receive Mileage Plus points on the transaction. Click "Confirm Purchase" to complete the transaction.