You can transfer your Citi Thank You rewards points to participating travel loyalty programs. One transferee is Air France/KLM Flying Blue. Citi Thank You rewards transfer to Flying Blue points at a rate of 1:1, so 1,000 Thank You points would yield 1000 Flying Blue points.
There is currently a limited time offer through August 29, 2018, where you can transfer ThankYou points to Flying Blue and receive 30% bonus points. So now you will get 1,300 Flying Blue points when you transfer in 1,000 Thank You points.