i booked DFW-JFK-MAD on DL/UX using FlyingBlue miles for 72k + $15.60.

i booked it as a one-way bc I couldn’t find return flights at the time. Let’s call this Reservation A.

I just found seats on DL for MAD-JFK-DFW, but AF charges £280 in YQ if I book it as a separate trip. This is bc the new trip originates in Europe. Let’s call this Reservarion B.

It is my understanding AF doesn’t charge YQ on RT DL flights when originating in the US.

it is possible for me to change Reservation A from a OW ticket and turn it into RT ticket by adding Reservation B? This would allow me to avoid the YQ when originating in Europe