One of the things that Donald Trump tried to negotiate in this trade deal, was better access to Canadian markets for US airlines.
Right now when an American carrier flies from Miami to Toronto, it can't go back to the U.S.A. via Winnipeg-Calgary-Seattle (as an example) and offer cheap short-haul flights to Canadians.
The US airline market is clearly better for everyday travelers on price and choice. The gap is large on short domestic trips and smaller on long-haul comfort.
Costs are the sharpest difference. Canada’s taxes, airport improvement fees, security charges, and navigation fees are far higher. Air Canada’s own figures put average domestic base fares in a similar range on both sides of the border, so the extra fees is what makes Canadian tickets expensive. Recent data also showed Canadian domestic averages rising into the high C$500s to about C$700, while US domestic averages sit around the mid-US$200s for a typical ticket that often covers longer distances.
Competition drives that gap. The US has four large network or high-frequency carriers (American, Delta, United, Southwest) plus real low-cost and ultra-low-cost options (Frontier, Allegiant, JetBlue, Breeze, and others). No carrier holds a dominant national share. Here, Air Canada and WestJet still account for most domestic capacity; Porter, Flair, and smaller regionals add pressure mainly on a limited set of city pairs. Many Canadian routes have one or two nonstops; many US city pairs have three or more.
Cabin classes are closer. Both markets offer basic economy, standard economy, premium economy, and lie-flat business on long-haul. But US carriers field more ultra-cheap bare-bones seats and, because of scale, more routes with premium cabins, lounges, and frequent-flyer redemption options. Air Canada might be competitive on major international routes, but the everyday Canadian flyer sees fewer fare brands and fewer luxury seats on domestic trips.
Carney is not protecting Canadians by refusing to allow US airlines onto domestic flights, he's promoting a monopoly.