In this photo provided by Ralph Usbeck an unidentified traveller runs in a smoke filled terminal at Brussels Airport, in Brussels after explosions Tuesday, March 22, 2016. Authorities locked down the Belgian capital on Tuesday after explosions rocked the Brussels airport and subway system, killing a number of people and injuring many more. Belgium raised its terror alert to its highest level, diverting arriving planes and trains and ordering people to stay where they were. Airports across Europe tightened security. (Ralph Usbeck via AP)