• American Airlines will launch new longer-haul routes from LaGuardia. They'll only fly once weekly.
• LaGuardia's new routes are doable thanks to the "perimeter rule" being waived on Saturdays.
• American and other airlines also use perimeter rule exemptions in Washington, DC.

American Airlines will use a special rule exception to fly longer-than-normal routes out of New York's LaGuardia Airport next year.

An airline spokesperson confirmed to Business Insider on Monday that American will launch new flights to Bozeman and Kalispell in Montana and Calgary in Canada in June 2025 to target leisure travelers.

There is one caveat: The routes will only operate on Saturdays.

This is because, to manage airport capacity, LaGuardia allows flights of only 1,500 miles or fewer from Sunday through Friday. This is known as a "perimeter rule." Longer flights and bigger jets are primarily pushed to the nearby Newark Liberty and John F. Kennedy airports.

However, the rule is waived for flights to Denver at all times and for flights operated to all other places on Saturdays. The latter exception gave American the leeway it needed to fly the new Saturday routes to Montana and Canada.

LaGurdia's slot restriction is also waived on Saturdays, meaning American won't need special takeoff and landing permissions for the routes. Cirium data shows all three flights will use a Boeing 737 Max and trek about 2,000 miles.

Operating Saturday-only flights to avoid the perimeter rule at LaGuardia is not new, though airlines have struggled to fill planes because Saturdays are lower-demand days.

Delta Air Lines, for example, cut two Saturday cross-country flights from LaGuardia to Los Angeles and Phoenix in January.

American also uses perimeter exemptions in the US capital

Ronald Reagan Washington National Airport in Washington, DC, is the only other US airport with a mandated perimeter rule. The restrictions at both airports were established in the 1980s.

Reagan's routes are limited to 1,250 miles. Dulles International Airport, about 30 miles away, gets longer flights.

However, over the past two decades, Congress has increased daily slot allowances to allow for more flights beyond the perimeter on Sunday through Friday.

American and other airlines have taken advantage of the exemptions. Cirium shows American already flies daily to Las Vegas, Los Angeles, and Phoenix.

Alaska Airlines, Delta Air Lines, Frontier Airlines, Southwest Airlines, and United Airlines also use exemptions to fly daily from Reagan to cities like Los Angeles, San Francisco, Austin, Denver, and Seattle.

The Federal Aviation Administration Reauthorization Bill, signed in May, approved 10 additional slots that could operate within or beyond Reagan's perimeter. That equates to five more roundtrip flights.

American was awarded one of the slots on Friday, a daily roundtrip to San Antonio starting in March. It will be the only airline operating the flight.

Meanwhile, Delta was awarded a slot pair to Seattle, Alaska was given one to San Diego, Southwest will use one to serve Las Vegas, and United received approval to San Francisco — which will be the airline's second daily flight to the California city.

There is debate over keeping the perimeter rule at Reagan and LaGuardia.

Some advocates say it reduces noise and airport congestion and ensures airlines don't shift slots to abandon regional routes within the perimeter. A near-miss at Reagan in May also sparked concern that more flights could impact runway safety.

Opponents of the rule say it restricts airline networks, gives travelers less choice, raises airfares, and limits economic growth. For lawmakers, eliminating the rule at Reagan would mean more convenient flights into DC from their home states.