Frontier Airlines announced its 100th overall destination Tuesday as part of a broader six-route expansion.

The milestone new city: Harlingen, from where Frontier will add routes to Chicago O’Hare and Denver from the city’s Valley International Airport. Harlingen is in far south Texas, about 20 miles north of the Mexican border and 45 miles west of the popular Texas beach destination of South Padre Island. 

Elsewhere, Frontier turned to Las Vegas for two seasonal routes to Mexico that will begin this winter. Frontier will be the only carrier flying to those destinations – Cancun and Cabo san Lucas – out of Las Vegas. And, while Las Vegas’ McCarran International Airport does have service to Mexico on some Mexican carriers, Frontier will be the only U.S. airline flying Mexican routes from Las Vegas.

The last of the six routes announced by Frontier each connect a cold-weather northern city to a warm-weather destination during the company's winter schedule. Flights between Chicago O’Hare and Palm Springs, California, begin Dec. 14, while Philadelphia gets a nonstop link to Sarasota, Florida, starting Dec. 10. Frontier will offer two flights a week on each of those routes.

Frontier did not detail any route reductions in announcing the six new options, but the carrier is well-known for quickly – and often quietly – dropping routes that do not meet its expectations. Some are discontinued “seasonally” with no firm plans to resume the service.

Along with Spirit and Allegiant, Frontier is one of the USA’s three big “ultra low-cost carriers.” Those carriers – along with Sun Country, which is currently adopting the model – are known for offering rock-bottom base fares but charging extra for nearly everything else beyond boarding the aircraft.

Scroll down for the schedule details on Frontier’s six newest routes: 

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Chicago O’Hare – Harlingen, Texas

Seasonal service begins Nov. 21; two weekly flights on Airbus A320 aircraft

Direct competition: None

Chicago O’Hare – Palm Springs, California

Seasonal service begins Dec. 14; two weekly flights on Airbus A320 aircraft

Direct competition: American, United

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Denver – Harlingen, Texas

Seasonal service begins Nov. 22; three weekly flights on Airbus A320 aircraft

Direct competition: None

Las Vegas – Los Cabos, Mexico

Seasonal service begins Dec. 15; Saturday-only service on Airbus A320 aircraft

Direct competition: None

Las Vegas – Cancun, Mexico

Seasonal service begins Dec. 21; two weekly flights on Airbus A320 aircraft

Direct competition: None

Philadelphia – Sarasota, Florida

Seasonal service begins Dec. 10; two weekly flights on Airbus A320 aircraft

Direct competition: None

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2017 09 Airbus 1500 Gallery 24
Frontier Airlines jets at Denver International Airport in July 2017.
Jeremy Dwyer-Lindgren, special to USA TODAY