Yes, you can use United MileagePlus miles to book flights on Air Canada, as both airlines are founding members of the Star Alliance. In 2026, this remains one of the most popular ways to travel between the US and Canada or on Air Canada's international routes. To book, simply go to United.com or use the United app, select "Book with miles," and search for your desired route. If there is "Saver Award" availability on an Air Canada flight, it will appear in the search results. A major benefit of using United miles for Air Canada flights is that United does not pass on fuel surcharges, which can save you hundreds of dollars compared to booking the same flight with Air Canada’s own Aeroplan points. Additionally, by April 2026, the new United MileagePlus Neo World Elite Mastercard in Canada has made it even easier for Canadian residents to earn miles specifically for use across the Star Alliance network. Just remember that award space on Air Canada’s "Signature Class" (Business) is often limited, so booking 8–11 months in advance is highly recommended.