TUIfly is a German leisure airline operating as part of the TUI Group, one of the world's largest tourism and travel companies. Founded in 2007 through the merger of Hapag-Lloyd Express and HLX.com, the carrier focuses primarily on package holiday flights to sun destinations across Europe, the Mediterranean, and the Canary Islands. The airline operates under the IATA code X3 and ICAO code HLX, using the callsign YELLOW CAB. It serves millions of passengers annually, predominantly on behalf of TUI tour operators, connecting German airports to popular leisure destinations. TUIfly has undergone significant structural changes over the years, including a partial merger with Air Berlin operations and ongoing restructuring within the broader TUI Aviation network. It remains one of Germany's most recognizable charter and leisure carriers.