What airline is the best for flying to Canada from the US?

I want to be in Canada for a few days beginning of July 2019 this year. I'm flying from Denver or maybe Las Vegas I'm wondering which airlines are people s favorite for flying to Canada.

United or Delta.

Virgin

Canada is rather large and has many Airports. It does matter if your final destination is on the east or west coast, the far North or someplace in the Middle.

FROM Denver
Air Canada to Montreal/ Toronto
Frontier to Calgary
United to Toronto Vancouver Calgary Edmonton Winnipeg
WestJet to Calgary.

FROM VEGAS
Air Canada
Flair Airlines (a Newer one)
Frontier
Swoop (Low Fares)
WestJet

For direct non stop flights to Canada. IF you want to connect a few more options. Really depends where in Canada you want to go.

Expect premium prices in July

If you just want to cross the Border for a short time you could fly to Detroit and take a transit bus over the Border for an outing. Shuttle Bus will take you Canada from the Buffalo Airport.
BEST for you depends WHERE you want to go and either regular fare or some low cost Airline fare.

Tell you what to do: find out which airlines fly from where you are to where you want to go. You can do that by googling to find a list of flights between your destination cities ('denver to vancouver flights', for example), seeing what airlines operate them. Or you can google for the website of the airport at either end, find the list of departures, and see which airlines are operating flights to where you want to go. Once you know which airlines go there, get back to us with a list of them and then we can choose one or two for you.

Speaking as a Canadian, I choose Westjet whenever they fly where I want to go. Among US airlines, I don't really care except that I'd prefer not to use United. Southwest often has the best prices in the US, but I don't think they fly into Canada. Sometimes, Canadians and Americans use the closest US airport to their Canadian destination or departure point and then use ground transport for the rest of the trip. It can work out cheaper, if a bit slower. That really only works for Vancouver/Seattle/Bellingham and Toronto/Buffalo.

The best airline is the one that is the least expensive and has the most convenient flights for you.

It's not a long flight so really the only thing that matters to most people is price and additional fees.

Delta.

That depends on where in Canada you would be flying to but even if you're crossing the continent, flights are generally not over 5 hours to most of eastern Canada, even if you're flying from the western US as long you fly direct.

So I would suggest whomever gives you the best price. But as far as comfort is concerned, I would say Westjet is the best out of the North American airlines. Air Canada is good as long as it's an Air Canada flight. Air Canada Rouge is their discount carrier and it's not as nice ( think sardine-like seating ). Unfortunately AC Rouge handles much of the North American routes.

Air Canada, United Airlines & Delta fly the most frequently from United States to Canada. The most popular route is New York to Vancouver, and Cathay Pacific flies this route the most.

I flew Air Canada from the US to Canada and then into China. They have pretty good service and have won awards for best North American airline.