From Brussels Airlines website:
Strike action by the Brussels Airlines pilots on 18 November 2013
Last update: 15h15
Due to a wildcat strike action of a number of our pilots, we are forced to cancel some of our flights on Monday 18 November. Our priority is to assist our passengers as much as possible. All customers affected by the strike action will be offered travel alternatives, depending on their travel needs.
http://www.brusselsairlines.com/en_be/misc/flight_disruptions2.aspx