So today I noticed that my return flight had dropped by $21/person. Called SW and they told me how easy it is for me to change my reservation online, which I did - quick and painless. 
Now I have a $42 credit, with no current plans to fly anywhere else in the next 11 months. Is it possible to apply it to Early Bird Check In for the flight I have booked now? I just went through the steps to try it, but I stopped when it asked me for a credit card number.
I was thinking maybe I will be able to, but just not yet. Maybe I have to wait a certain amount of time for my $42 credit to be processed...?
Anybody know about this?
Thanks!

Now I have a $42 credit, with no current plans to fly anywhere else in the next 11 months. Is it possible to apply it to Early Bird Check In for the flight I have booked now? I just went through the steps to try it, but I stopped when it asked me for a credit card number.
I was thinking maybe I will be able to, but just not yet. Maybe I have to wait a certain amount of time for my $42 credit to be processed...?
Anybody know about this?
Thanks!