Turf war: 2 US airlines go head-to-head with major expansions in Puerto Rico

The mercury is rising in Puerto Rico, and that's not necessarily because spring is approaching.

Instead, a heated turf war for dominance in the territory's aviation market appears to be unfolding between America's two largest ultra-low-cost carriers.

Spirit Airlines announced Wednesday that it's adding five new routes and boosting service on four others to San Juan's Luis Muñoz Marín International Airport (SJU), as you can see in the table below.

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Once the new service launches, Spirit will become the second-largest carrier by destinations, seats and available seat miles to the island territory.

By June, the Miramar, Florida-based carrier will offer up to 21 daily departures from San Juan. Overall, Spirit will now serve 16 total nonstop routes from the three airports it serves in the territory.

"Spirit Airlines has served the Puerto Rican community for more than two decades, offering affordable fares to connect family and friends across the United States," John Kirby, vice president of network planning, said in a statement. "Puerto Rico is our number one destination in the Caribbean, with its rich history and culture, renowned beaches, tropical rainforest and the world's brightest bioluminescent bay."

Spirit first landed on the island in 2001 with service to San Juan and has since grown its Puerto Rico route map to include Aguadilla in 2007 and Ponce, returning to the latter in 2022 after previously serving it from 2007 to 2008.

As part of Wednesday's announcement, the airline was also keen to mention its involvement in the local community, which includes work with multiple nonprofits and donations of over $100,000 for hurricane relief efforts.

While Puerto Rico has long been a popular destination in the Caribbean, Spirit's latest expansion there comes on the heels of a similar announcement from one of its biggest rivals, Frontier Airlines.

Two weeks ago, Frontier announced its own major expansion in the territory, with the addition of eight new routes, all launching in May, as you can see in the table below.

With these new flights, Frontier will offer a total of 19 nonstop routes to the island, crowning the airline as the largest carrier serving Puerto Rico by the number of markets served.

Frontier's expansion perhaps caught the attention of the network planners at Spirit, who weren't ready to let one of its no-frills competitors gain a share in a key market.

So, it's likely no surprise that Spirit is retaliating by adding new or expanded service in all but one of the new San Juan markets that were just announced by Frontier. Additionally, Spirit is adding a route from San Juan to Atlanta, which happens to be one of Frontier's biggest focus cities.

Further pushing back against its rival, Spirit will launch most of its new flights on May 5, just one day after Frontier's big expansion commences.

It'll be interesting to see whether the two airlines can maintain all this new service. However, the biggest winners are travelers who are looking for cheap tickets to and from Puerto Rico.

Related: 8 reasons to visit Puerto Rico in 2023

Frontier's expansion came with introductory fares starting at $49, and now Spirit's new flights will start at just $59.

Of course, whichever airline you choose, you'll be on the hook for what could be hundreds of dollars in additional fees for seat assignments, bags, changes and more.

In terms of the passenger experience, Spirit definitely has the upper hand — the airline offers (nearly) fleetwide Wi-Fi, as well as the ability to purchase spacious and comfortable Big Front Seats.

That said, Frontier is poised to become Puerto Rico's largest carrier, but Spirit is busy closing that gap.