We take the 10:00pm red eye from SEA to CLT then to SXM. Arrive 11:30 Saturday morn in SXM. All on American Air miles. Love it. Then leave SXM at 9am and arrive in SEA same day at 8:00pm. All on miles. Already booked for next May-June.
Miles on AA have always worked for us.
I use my Alaska Air miles for domestic flights with no problems either.