Please be aware that Brussels has multiple airports and that these results are for all airports serving the city.
The best month to fly between Brussels and Madrid is January and the most expensive month to fly is March. (Average prices, based on 308 datapoints.)
The best day to arrive at Brussels is Thursday and it would be best to avoid Sunday, as prices are on average 109.38% higher than on Thursday. (Average prices, based on 266 datapoints.)
The cheapest airline flying from Brussels to Madrid is Ryanair. They are 40% cheaper than Brussels Airlines. (Average prices, based on 315 datapoints.)
The best time to fly is at around 15. (Average prices, based on 449 datapoints.)