Americans flying from Montreal to US. Flight at YUL 9:00 AM on a Sunday morning. What time do we need to leave from hotel downtown? Or should we stay near the airport Saturday night? Thanks.

Based on my experience flying from Toronto to the US it would surprise me if Sunday morning is a busy time for flights to the US at YUL. Traffic should be very light so figure 20-25 minutes for the taxi ride. I would aim for being at the airport 90 minutes ahead of the flight. This is what Air Canada recommends for flights to the US. AC says the cut off is 60 minutes. Remember that you must clear US customs and immigration in Montreal. Most likely this will get you there with of time to spare but there is always the chance of something going wrong. Staying near the airport would mean missing the chance for a lovely meal at one of Montreal's great restaurants.

I often fly from Montreal. For a US flight I like to be at the airport two hours before flight departure. So, I wld leave my downtown Montreal hotel @ 6:30AM for a 9:00AM departure. Check-in, then go & have breakfast.
Enjoy Montreal! I love that city! When will you be there?

We're leaving Montreal on Sunday, September 14th, after a cruise from NYC to Quebec city. Taking the train from Quebec to Montreal and spending a couple nights there. Plans are taking shape nicely, but I'm sorry I waited to book our one way flight from Montreal - price went up $100 since last month. Thanks for the advice.

Schnitzel, That $100 is probably a fuel surcharge. What airline are you flying? When I fly Toronto/Montreal on Air Canada the fares go up & down & up & down on a daily, & sometimes hourly, basis. If you have the time & the patience, you can grab a pretty decent fare if you keep monitoring the fares.
So, even with the added fuel surcharge you may actually end up paying less than you wld have a month ago if you wait & grab a low fare when you see it. In "the old days", the earlier you booked, the lower the fare but that is not always the case today when fares fluctuate hourly just like the stock market.

You're right about these roller coaster airline prices. I booked last night on UA after the price went down $60. We're set to go!

Well, that is just great, Schnitzel! Enjoy your cruise. September is a beautiful time to be in Montreal & Quebec City!