If the CUN-BOS is indeed seasonal, then just cut out the BOS-JFK segment and do CUN-MIA-BOS or CUN-DFW-BOS. You can get from Boston to New York on the train for a lot less hassle than flying and probably shorter in time. And it will drop you at Penn Station, which is more or less in the middle of the city as opposed to dealing with Kennedy which I find is usually/always a nightmare. The Acela Express in biz is nice. The standard coach is fine if the train isn't crowded. Never been in or seen the Acela first class.