As one of the world’s largest and most populous countries, the United States of America has long had a vibrant and diverse domestic aviation scene. According to current data made available by Cirium, an aviation analytics company, its airlines have scheduled 717,808 internal flights this October.
These flights will serve a huge range of destinations, with a correspondingly wide variety of airlines and aircraft being used to operate the services in question. Collectively, they will offer whopping grand totals of 92,838,138 seats and 83,459,383,168 available seat miles (ASMs), but which US domestic routes are the busiest? Let’s examine the data and find out, using the metrics of flights, seats, and ASMs.
By Frequency
The internal route from Ted Stevens Anchorage International (ANC) to Kenai Municipal Airport (ENA) in Alaska doesn’t scratch the surface as far as the US’s top domestic routes by seats and ASMs are concerned. However, the 60-mile (96.6 km) hop is served so often that it comes out as the country’s busiest route by flight frequency this October, with 1,167 departures from Anchorage and 1,162 from Kenai.
Sterling Airways serves this corridor twice a day with the Saab 2000, while Kenai Aviation averages just under 12 daily rotations with its Tecnam P2012s. However, Grant Aviation is the route’s main operator, with as many as 27 round trips a day using its Cessna 208 Caravan aircraft, some of which it acquired from Ravn Alaska following its bankruptcy in 2020. The airline also offers bespoke journeys, and says:
“In addition to our scheduled flights, Grant Aviation offers charter flight services. (…) A charter includes the entire aircraft and your pilot for the amount of time necessary to reach your desired destination.”
By Seats
The US domestic route that offers the most seats this October is one that you are much more likely to have traveled on than the Alaskan hop mentioned above. Indeed, the corridor in question covers the 733 miles between New York’s 
LaGuardia Airport (LGA) and Chicago O’Hare International (ORD).
This month, four different major US airlines will combine to offer 159,892 seats from LaGuardia to O’Hare and 159,848 seats coming back, with this capacity spread across 1,025 flights in each direction. All of the ‘big three’ US legacy carriers serve this route (American Airlines, Delta Air Lines, and United Airlines), but the fourth spot is occupied by a rather different operator, namely ultra-low-cost carrier Spirit.
Spirit has the fewest flights, with daily rotations from October 1 to 25 that will rise to twice a day at the end of the month as the IATA Winter Schedule begins. Meanwhile, Delta has penciled in 251 round trips across the month (between four and nine a day), followed by American with 295 (between six and 10 a day, including some with its regional partners) and United with 441 (between nine and 15 a day).
By Available Seat Miles
When it comes to ranking routes by available seat miles, transcontinental routes tend to come out on top even if they are operated with lower frequencies, due to the fact that they are further and the aircraft that carriers use to serve them tend to have more seats on board. This rings true in October, with the busiest US domestic route by ASMs linking 
New York JFK Airport with Los Angeles International (LAX).
This month, four airlines have scheduled 897 flights each way on this lucrative and popular route across the country, with more than 153,000 seats and 379 million available seat miles offered in each direction. Legacy service comes from American and Delta, with JetBlue and Frontier being the others.
The latter has the lowest frequency, with just a single daily rotation throughout the month. However, the rest are quite closely packed, with American Airlines operating 279 round trips, followed by Delta on 289 and JetBlue on 297. Despite not operating the most flights, Delta has the most seats and ASMs on this route in October 2025, as it primarily deploys widebody aircraft with more seats, like the Boeing 767.
