These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Incheon Intl Airport to Albury Airport flight would often be abbreviated as a ICN to ABX flight. This flight route has multiple associated airports, so we think it might be helpful to learn the name and codes of them as well. They are Bangkok Suvarnabhumi Airport (BKK), Manila Ninoy Aquino Intl Airport (MNL), New Delhi Indira Gandhi Intl Airport (DEL), Singapore Changi Airport (SIN), Kuala Lumpur Intl Airport (KUL).