Great question - CRK to MAD just means Angeles City Clark Intl Airport to Madrid Barajas Airport. Now you’ll know what these unique codes when you look for flights! While you’re still figuring out your travel plans, it’s not a bad idea to learn the names and codes of other airports around these areas: Barcelona-El Prat Airport (BCN), Malaga Airport (AGP), Palma de Mallorca Son Sant Joan Airport (PMI), Alicante Airport (ALC), Valencia Airport (VLC).