Excellent deals right from Montreal to Paris with Air Transat at just US$142 (now showing as low as $125 for some dates) for the Round Trip. (HT Flyertalk)
Fares seem to be bookable on many different sites including Orbitz.com. I searched for fares this fall.
This deal won’t last so book quickly and make use f the 24 hour free cancellation if you need to.