To get back to the OP's actual question (!), according to JFK ground staff the cancellations were due to light loads and not to any tech problems. The baggage disaster at T4 last week may have hit J bookings, plus it's February so loads aren't brilliant. (My two transatlantics over the past few days were only around 1/2-2/3 full in J at popular departure times. Busy in F though.)