Yes, they issue a credit. You have to call them though and let them know that you know your fare is lower. They won't do it automatically. We have to use the credit that we got from Jetblue to book a flight within the year from when the credit was issued. When all was said and done with ups and downs of our fare before the trip, we ended up getting $210.00 in credit that we need to use to book a flight before it expires! Jet Blue customer service is the best!!! Hope that helps!