*A from US to Europe to Canada for cheap in Fall. Look for booking class K on SN-coded transatlantic flights. The rules allow many variations in regards to routing.

Example for just USD 459 ai:
Nov 11 EWR-BRU-LIN (Linate, Milano, Italy) SN KLXNC7NS
Dec 14: BRU-YUL SN KLXRCT06

All on SN codes. EWR-BRU is op UA, BRU-LIN is op SN, BRU-YUL is op AC.

You can add onwards flight within Canada on AC/ACx with AC-code or SN-code (wherever you find K availability) for little extra. For example, adding YUL-YHZ will add USD 40. In that example, you'd travel 8053 miles for USD 499. You can sneak in a night in YUL, as long as you continue within 24 hours.

Transatlantic sectors can be any day except Friday and Saturday. Fare is valid Oct 16 to Dec 10 and Dec 24 to May 06 (?) for the outbound transatlantic sector. You may fly back during the "blackout" period.

Round-trip fare can be constructed on the basis of two half roundtrips (hence the double open jaw). Sunday rule applies.

Feeder/connector flights in North America have to be SN, UA or AC coded (with various operators permitted, including some non-*A). Feeder/connector flights in Europe have to be coded on SN/LH/LX/OS/4U/JP/SK/TP/LO/OU with varying operators permitted (no A3 nor TK, but some non-*A-operators are allowed).

1 FREE STOPOVER PERMITTED ON THE PRICING UNIT IN BRU/DUS/
FRA/GVA/LON/MUC/PAR/VIE/ZRH/MIL/CPH/DUB/EDI/MAN.
OR - 1 FREE STOPOVER PERMITTED ON THE PRICING UNIT IN BCN/
LIS/MAD/VCE/ATH/IST.

5 TRANSFERS PERMITTED IN EACH DIRECTION FREE
3 FREE IN AREA 2/AREA 3 IN EACH DIRECTION
2 FREE IN AREA 1 IN EACH DIRECTION

To be found on ITA Matrix and Hipmunk. Hipmunk will lead you to an OTAs that can priced it out and have it issued.

Good luck hunting!