You may not want to have any miles on Aeroplan after trying their website for nonstop flights which can add up to many additional FF miles than normal. I've been a UA member living in Toronto and have done most of my miles bookings with UA for AC flights. To Europe you will find UA wants 105000 miles compared to 80000 from Aeroplan but the difference is meaningless if you have to fork out more miles if return nonstop flights are preferred. I have found ANA site good for screening available *A FF flights before calling UA to book.