Why it's cheaper in the US
Departure taxes and fees are often lower on the US side, and low-cost carrier competition is stronger. Hence sometimes much cheaper flights.
Border airports near Quebec
From Montreal, Plattsburgh (~1h) and Burlington (~1.5h) give access to cheap US flights, especially to Florida.
What to plan for
Valid passport, arrive 3h early (US customs), and factor in airport parking. Add it all up before concluding it's really cheaper.
When it's NOT worth it
If the saving is small, driving time + parking + risk can wipe out the gain. Always compare with a direct Canadian departure.
FAQ
Do I need a passport to fly from the US?
Yes, to cross the border and for an international flight.
Which US airport is closest to Montreal?
Plattsburgh (NY), about 1 hour away.