Re: fish flights
Is the existing 5400' runway at New Bedford long enough for those international flights?
The answer to that depends on trading cargo weight for fuel.
According to Boeing's fact sheet on the 757-200F (Icelandair's cargo plane), EWB-KEF's great circle distance of 2,130 nm is approx. 40% the maximum range of the aircraft. Assuming that you fill the plane near to its maximum take-off weight (MTOW), it requires somewhere between 7,000 and 9,000 feet to take off, depending on which engines Icelandair has installed.
HOWEVER, you might not be anywhere near MTOW. Fish is valuable by weight, which means it may be economical for the airline to send half-full planes half the maximum range. Under those assumptions, I bet 5,400' is enough.
Also, the last round of plans for airport expansion at New Bedford and the construction of a full-on cargo hub assumed extension of both runways into the 8,000' range. That would resolve any issues. That proposal failed because of local opposition to jet noise and impacts to the marsh north of the field. A more limited Iceland-only service would use quieter aircraft and require less or no runway extension, so it might have legs.
Also, Logan has less than zero cargo capacity remaining (literally, since they're at capacity and removing cargo space for Terminal E). MA needs EWB to do more, especially since it's so beautifully positioned for intermodal transfers.
Btw, Amazon also has an airline now, and their big warehouse is conveniently located in Fall River, and Baker's going to want any benefits/subsidies for HQ2 to benefit the whole Commonwealth, so...