Frontier Airlines is offering a limited time promotion for flights between Philadelphia and Pittsburgh

Low-cost airline is selling round-trip flights between Philly and Pittsburgh for as low as $36.50. Frontier said it's a promotional deal as it launches a cross-commonwealth service. For a limited time, the airline is offering round trip seats for $36.

Frontier Airlines is expanding service out of Philadelphia International Airport. The airline will fly to Norfolk, Virginia and Buffalo, New York this summer. Service on both routes will begin in early June. Service will be offered to Norfolk and Buffalo starting this summer, starting in early summer.