You can transfer your Citi Thank You rewards points to participating travel loyalty programs. One transferee is Air France Flying Blue. Citi Thank You rewards transfer to Flying Blue at a rate of 1:1, so 1,000 ThankYou Points would yield 1,000 Flying Blue Miles.
There is currently a limited time offer through July 20, 2019, where you can transfer ThankYou points to Flying Blue and receive a 25% bonus. So now you will get 1,250 Flying Blue Miles when you transfer 1,000 Thank You points.