United Airlines will add three new domestic routes at its Denver hub.

Daily flights to Greenville/Spartanburg, South Carolina, and Syracuse, New York, will begin June 6 and will operate year-round. Flights to Portland, Maine, start June 8, but they’ll operate only on weekends during the summer schedule. (Scroll down for full schedule details)

All three of the new routes will go head-to-head against service offered by Denver-based budget rival Frontier Airlines.

The routes add to other previously announced United routes to Charleston, South Carolina; Eureka, California; and Fairbanks, Alaska. Those flights also begin June 6.

In other details announced Thursday, United will expand its existing weekend-only summer service to Burlington, Vermont; Savannah, Georgia; and Pensacola in Florida. A Sunday round-trip flight is being added to those routes, which currently fly only on Saturdays.

Also getting more flights will be United’s service between Denver and Fort Myers, Florida. The route previously operated only during the winter, but will now be offered Saturdays and Sundays during the summer and fall until daily service resumes as scheduled in October.

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The latest routes were announced the same day that United put its new “rebanked” schedule into effect at Denver. The airline has tweaked schedules on its “banks” of incoming and outgoing flights, trying to better match connecting passengers with flights.

United says the schedule adjustment – which began Thursday (Feb. 14) – will boost the number of morning flights available to business customers traveling from Denver to the East and West coasts while also improving connecting options for customers traveling to or from the airline’s Midwest and Mountain Region destinations. The effort was first announced last fall.

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“As we build on the strengths of our mid-continent hubs, United’s optimized schedule along with the growth in destinations offered and frequency of flights allows us to deliver on what’s best for our customers - more flights and greater access to more of the places they want to go than ever before,” Ankit Gupta, United’s vice president of domestic network planning, said in a statement.

Steve Jaquith, vice president of United’s Denver hub, said Denver was “United’s fastest-growing hub, with a record of more than 500 daily departures this summer.”

“With the enhanced schedule, we’ll reduce the amount of time customers will spend waiting at the airport

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and provide better options to customers arriving on flights from smaller markets to get to destinations east and west of Denver,” he added.

United has already rebanked its schedules at its hubs at Chicago O’Hare and Houston Bush Intercontinental.

Schedule details for United’s three newest Denver routes are below.

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Denver-Greenville/Spartanburg, South Carolina

Begins June 6. One daily round-trip flight on Embraer E175 jets operated by United Express affiliate SkyWest.

Direct competition: Frontier Airlines.

Denver-Syracuse, New York

Begins June 6. One daily round-trip flight on Embraer E175 jets operated by United Express affiliate SkyWest.

Direct competition: Frontier Airlines (seasonal).

Denver-Portland, Maine

Begins June 6. One daily round-trip flight on Airbus A320 jets.

Direct competition: Frontier Airlines (seasonal).

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