Was this the EI 137 by any chance ?
I ask, as we were booked DUB-BOS on the 137, as part of a larger EI/B6 itinerary for later in the month (Nov 24th) & got an eMail from Aer Lingus a couple of weeks ago, saying there was a change in schedule & to contact them. When we did, we found out that the 137 had been cancelled, leaving only the 139 flying that day. So we ended up getting a full refund & booking with BA via LHR.
So loads must be very much down on the BOS route, if they're dropping flights from the schedule & your experience of the flight on Monday being virtually empty, seems to confirm this !