| Abbreviation | Designation | |
|---|---|---|
| FLX | FlixTrain, FlixTrain GmbH (German) | railway company |
| HKX | Hamburg-Köln-Express, Hamburg-Köln-Express GmbH (German) | railway company |
| HKX | Hamburg-Köln-Express (German) | train category |
| HKX | Hamburg-Köln-Express (Hamburg-Altona b/w Köln ↔ Frankfurt) (German) | transportation line |
| HKX | Hamburg-Köln-Express (Hamburg-Altona b/w Köln) (German) | transportation line |