Northwest canceled 500 flights over the weekend, due either to pilots acting improperly (according to management) or pilots not being scheduled correctly (according to the pilot’s union). For several months now, pilots have hit their 90 hour flight limit (please do not write saying that this is a small number of hours to work for the month. Flying hours only count the actual number of hours in the air plus taxiing) early in the month, leaving a shortage of pilots. Northwest won’t hire more, which is upsetting the union.
In any case, while it’s a small number of the total flights, if you have a Northwest flight booked late in the month you should call the airline the day before to make sure it’s actually flying.