The most frequent international flights out of the US don't cross an ocean — they cross a border. Cirium frequency data for 2026 shows LaGuardia to Toronto Pearson at number one with 7,901 annual departures, about 22 a day, nudging out the famous New York JFK to London Heathrow corridor (7,338 departures) for the top spot.
Canada dominates the rankings overall. Four of the nine busiest US international routes connect to Canadian airports — LaGuardia, Chicago O'Hare and Newark to Toronto, plus Seattle-Tacoma to Vancouver — and together they log 23,463 flights, just over half the total of the entire top nine. That's notable given the current trade tensions between the two countries, which have already pushed Air Canada to drop its JFK-Toronto service and consolidate on Newark and LaGuardia, where United, American and Delta all compete. American flies the Chicago route with regional jets from Envoy Air, running up to five daily Embraer E170s and CRJ-700s because business travellers want schedule flexibility more than seat count.
Why does frequency favour these short hops? Aircraft maths. A narrowbody flying New York–Toronto or the 111-mile Seattle–Vancouver sector can squeeze in multiple round trips a day, while a JFK–Heathrow widebody is committed for the best part of a day per rotation. Seattle–Vancouver racked up 5,371 departures thanks to Delta, Alaska and Air Canada shuttling the same aircraft back and forth.
The quirk of the list is San Juan to St. Barts, sitting fifth with 5,103 flights — ahead of JFK–Paris. The Caribbean route is served by Tradewind Aviation and St. Barth Executive using 10-seat Pilatus PC-12s, because St. Barts' famously tricky short runway restricts the airport to small regional aircraft. High frequency is the only way to meet demand.
Latin America rounds out the rankings: Houston to Mexico City with 3,643 departures and Miami to Bogotá with 3,231. Both are year-round markets mixing business, leisure, VFR and connecting traffic rather than seasonal tourism, and each pits rival alliance hubs against each other — United's Star Alliance base versus SkyTeam's Mexico City, American's oneworld Miami gateway versus Avianca's Star Alliance Bogotá.
For travellers, the practical takeaway is plenty of choice. The New York–Toronto corridor alone is served by three US carriers plus Air Canada and Porter, and Seattle–Vancouver offers frequent shuttle-style service. Whether Canada keeps its grip on the leaderboard is a open question — airline fleet plans and the political climate both have a say — but for now, if you want to hop across a border often, these are the routes doing the heavy lifting.
