PRESQUE ISLE — The introduction of a third airline at the airport here has ignited a fare war that is cutting round-trip fares to Boston by more than half.

City councilors Monday approved a three-year contract allowing U.S. Air Express to fly out of Northern Maine Regional Airport. The new airline, which joins Northwest Airlink and Business Express, plans three daily flights to Boston beginning June 1.

The two existing carriers have recently lowered their fares to Boston by as much as $280 on a round-trip ticket. Schedules of U.S. Air Express fares already entered in the travel industry computer network offer a round trip to Boston beginning at $168. The existing carriers have lowered their rates for the same trip from about $450 to $173.50.

“They (U.S. Air) are already having an effect (on fares) and they’re not even here yet,” said Stephen Leighton, manager of American International Travel in Presque Isle.

Greg Willard, airport manger, is glad to see a new airline at NMRA.

“The situation at Loring has stabilized, and (U.S. Air and Presque Isle) think the county can support three airlines,” Willard said.

The economy has no where to go but up, he continued, and if a proposed resort and casino is approved as a re-use venture for Loring, there will be even more need for the third airline.