As was demonstrated yesterday in Turkey, and a couple of months ago in Brussels.....the unsecured areas of an airport (actually any mass transit station) are now a problem. Hundreds of people milling about in an open area, carrying luggage (that could contain anything), with their faces glued to their phones.
LOOK UP PEOPLE! Pay attention to your surroundings. Know where the exits are. If possible be armed, and if armed, be prepared TO STOP AN ATTACK!