US Airways announced Monday night that it has added a fifth daily flight to Philadelphia out of Tweed-New Haven Regional Airport.

The new flight is part of an airport-wide expansion that also includes aircraft upgrades, the construction of runway safety areas and increased marketing and promoting.

Airport Authority chairman Lawrence DeNardis said the expansion comes as a result of the increase in passengers since Delta Airlines began to offer jet service out of Tweed last May. In 2004, Tweed boarded 40,665 passengers, which is 146 percent more than in 2003.

“Once Delta was added, everyone benefited,” DeNardis said. “It was like a symbiotic relationship between US Airways and Delta. They are both thriving off each other, and basically it has been onward and upward at Tweed.”

US Airways also announced Monday that by March 6, 2005, it will upgrade one of its flights to a 50-seat Dash 8-300. The current aircraft can accommodate 37 passengers. By March, the Airport Authority plans to submit final design engineering plans for permits to build runway safety areas, which provide the foundation for additional take-off distance and would allow airlines to expand service to farther away destinations.

New Haven Mayor John DeStefano Jr. joined East Haven Mayor Joe Maturo, Vice President for New Haven and State Affairs Bruce Alexander and DeNardis for a press conference Monday reviewing Tweed’s success in 2004 and detailing new developments at the airport.

Tweed’s success is critical for New Haven and Southern Connecticut’s economy. Improving transportation infrastructure — rail, air and roads — is crucial for attracting jobs and helping working class families, DeStefano said.