BRUSSELS, BELGIUM - MARCH 22:  People hold up a banner as a mark of solidarity at the Place de la Bourse following today's attacks on March 22, 2016 in Brussels, Belgium. At least 31 people are thought to have been killed after Brussels airport and a Metro station were targeted by explosions. The attacks come just days after a key suspect in the Paris attacks, Salah Abdeslam, was captured in Brussels.  (Photo by Carl Court/Getty Images)