I have found lately that AC seems to cancel flights quickly, for questionable reasons. I have begun to believe it is a method for reducing to capacity, increasing seat miles. IE, they have 75 people booked to DCA on the Airbus, and 45 on the next flight, if weather will let them get away with cancelling one and operating full, I believe they try and do it. Others may say that really isn't possible with aircraft needing to be in certain places, crew sched ect... but I wouldn't be suprised.