What are the “low-cost” airports Norwegian could fly to?

Report analyses various options for cut-price transatlantic flights
As previously reported, Norwegian hopes to start thinner transatlantic routes and sell one-way tickets for just $69 from 2017. The CAPA Centre for Aviation speculates how this could be done. As Norwegian itself says, it can really only do this by flying to US airports that have low fees.
The airline’s already formidable presence at its bases in Scandinavia will deepen as it launches Las Vegas flights from Copenhagen and Stockholm in the coming winter season and Boston services from Copenhagen and Oslo in May 2016, as well as launching London-Boston.
Services to Baltimore/Washington are under consideration, as are flights from the Danish cities of Aalborg and Billund to New York (but probably not to JFK), using B737 MAX 8 aircraft, from 2017.
For cheaper airports in the northeastern USA, CAPA says that Stewart International Airport is a possibility, but it currently has poor surface connections to New York. Airlines such as Allegiant, American, Delta and US Airways operate at Stewart.
Atlantic City International Airport is an option, but it is remote from New York, 200km to the south. Westchester County Airport is within New York range, but it is close to residential neighbourhoods with a need for voluntary curfews.
With its location between New York and Boston, Hartford Bradley International Airport is a definite possibility. Connecticut Airport Authority recently said that negotiations with several carriers on transatlantic routes to the airport were “showing promise”.
Other “low-cost” airports that Norwegian could fly to are discussed in the CAPA report, which can be viewed here.