According to a DL insider over at airliners.net, the crew had worked ATL-JFK-BCN on Friday July 1 (instead of just JFK-BCN); the extra leg, coupled with the delays experienced at JFK on that day due to the weather, DL knew ahead of time that there would be crew legality issues on the return. That's why the BOS stop was scheduled on the return flight on July 3. However, due to strong headwinds on July 3 between BCN and JFK, they had to stop at BGR instead. In the end, DL95 only arrived JFK about 1hr 33 minutes late; not bad considering the situation.