Frontier Airlines, which has been aggressively expanding, announced new daily nonstop flights Wednesday from Philadelphia International Airport to Houston and Minneapolis, beginning April 30.

Introductory one-way fares of $59 to Houston and $49 to Minneapolis will be available through 11:59 p.m. Saturday at for travel on Tuesdays, Wednesdays, and Saturdays from April 30 to June 10. Seats will be limited at these fares.

The service will be seasonal until the fall. Frontier began flights in December to Miami, Orlando, and Tampa, and to Cancun, Mexico, from Philadelphia, and flights to Atlanta, Charlotte, and Chicago O'Hare are scheduled to begin next month.

Frontier flies to 10 cities from Trenton-Mercer Airport in Ewing Township and to two Florida cities from New Castle Airport in Delaware.

The Denver-based airline has been remaking itself as an "ultra-low-cost" airline. The base fares are cheap, but passengers pay extra to put a carry-on bag in the overhead bin ($30 at online check-in; $60 at the gate), for advance seat assignments ($3 to $8), and $2 for a soda and water on the plane.

Frontier filed for bankruptcy in 2008, was acquired by Republic Airways in 2009, and was sold in 2013 to a Phoenix private-equity and venture capital firm, Indigo Partners.

Indigo managing partner William Franke is the former chairman of Spirit Airlines, another carrier with low base fares. Over the last year, Frontier has been overhauling its route network and moving to the low-cost business model of Spirit.

Frontier handed pink slips last month to 1,300 employees - 1,160 of them in Denver - and said it was outsourcing the jobs to "partner" companies.

While the ticket agents, reservation agents, ramp personnel, and baggage handlers are expected to be offered jobs with contract vendors, the laid-off workers said the new jobs would likely pay less and have fewer benefits.

Frontier said the changes were "part of a comprehensive companywide strategy" to successfully compete as a low-cost airline, offering "customers much-needed relief from high airfares nationwide. Low fares are only achieved through low costs."

Philadelphia Airport CEO Mark Gale said: "This is great news for the traveling public in the Philadelphia region and beyond. More low-fare choices mean more competition, which is good for the consumer."

Airline analyst Hunter Keay, of Wolfe Research L.L.C., said in a client note: "Given Frontier's growing relevancy and aggressive capacity growth, we feel they matter more every day." Keay expects Frontier to grow 23 percent "year over year" in the current first quarter and to grow 20 percent annually through 2020.

The Houston flight will depart Philadelphia daily at 4:30 p.m., arriving in Houston at 7:10.

The Philadelphia flight will leave Houston at 6:50 p.m., arriving here at 11:10. The Minneapolis flight will depart Philadelphia at 2 p.m., arriving in Minneapolis at 3:50, and leave Minneapolis at 9:45 a.m., arriving in Philadelphia at 1:20 p.m.