I have a trip in March that I booked RT ANC-PDX-PHX in F, and PHX-ANC direct return in Y. I decided I will make a detour to SMF afterwards, but I am not sure if cancelling my return PHX-ANC leg will cause the entire RT fare to be re-priced. I just would assume wait until I fly to PHX to cancel the return leg. Is there any downside to this plan?

As an aside, I booked an AA award fare through AS for 9K miles in F PHX-SMF. Thought it was a mistake but it worked!


Edit: I realized the thread title is not very clear, what I should have said was "Cancelling return flight after outbound flight is completed"