SUB stands for Surabaya Juanda Airport, while MAD stands for Madrid Barajas Airport. These codes are often called IATA codes, a set of identifiers established by IATA (International Air Transport Association) that is widely used by airlines and the aviation industry. 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).