Error Fare flights from London, UK to Montreal, Canada for only £140 roundtrip with United Airlines.
Appears to be an OTA glitch.
WE STRONGLY RECOMMEND YOU DELAY MAKING FURTHER PLANS AS MUCH AS POSSIBLE.
BECAUSE THIS IS AN ERROR-FARE, THERE IS ALWAYS THE SMALL CHANCE THE AIRLINE MAY CANCEL THE TICKET.
Availability from October to December 2017
Allow the search to complete, then click an OTA to view the advertised price: