How can an airline offer such low airfares? Turns out, there are a few reasons.

Norwegian Air is bringing nonstop European flights to three small Northeast airports, adding 10 new trans-Atlantic routes that initially will go on sale for as little as $65 one way.

The fast-growing European discount carrier announced the expansion Thursday, revealing plans for five trans-Atlantic routes from Providence, four from Newburgh, N.Y., and one from Hartford, Conn. The new routes include destinations in Ireland, Northern Ireland and Scotland. (Scroll to bottom for schedule and route details)

The first of the new flights kick off in June, with Norwegian offering special introductory fares of $65 one-way to Europe. The special return fares will run €69 or £69, depending on the destination – though overseas taxes can add the equivalent of up to $200 on Norwegian’s U.S.-bound flights.

As of early Wednesday morning, the $65 fares (taxes included) to Europe showed fairly broad availability on Norwegian’s website — though the fares had largely dried up by mid-afternoon. While they lasted, the introductory return fares were roughly $80-$100 from the airports in Ireland and Northern Ireland, meaning some round trips had been available for less than $150 at the special fares. Return flights from Scotland started at about $226, making a…