These are just IATA (International Air Transport Association) codes. They are used in aviation to identify and differentiate airports. That’s why a Stockholm Arlanda Airport to Phuket City Airport flight would often be abbreviated as a ARN to HKT 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 Gothenburg Landvetter Airport (GOT), Stockholm Bromma Airport (BMA), Stockholm Skavsta Airport (NYO), Stockholm Vasteras/Hasslo Airport (VST), Luleå Kallax Airport (LLA).