There are plenty of other carriers and options available. When I was living in Brussels the only time I would fly would generally be if I was visiting our offices in Spain or in Italy. Everywhere else I would take the train - so Thalys to Paris or Düsseldorf, Eurostar to London, ICE to Frankfurt etc. Even with a 3 - 4 hour journey time via ICE from Brussels to Frankfurt it was generally quicker than flying!