I like it when international Airlines put up web sites in different languages.
When I search for a flight - let's say CGN to EWR - on the German website The airport names show up automatically in German e.g. Köln, Deutschland (CGN). This is also the case in the Neue Suche starten:: 'New search' section. Now, when I change the dates or the destination, the system doesn't recgognize Köln, Deutschland (CGN) as an airport and sends me to the Flight search site with an error message: ! Geben Sie einen gültigen Ort, Flughafen oder Flughafencode ein. : 'enter a valid location, airport or airport code'. This is somewhat annoying, at the website automatically expands CGN to the full German name and then doesn't recognize it afterwards. Same trouble with Düsseldorf, Deutschland (DUS)

The problem seems to be processing the letters ü, ö (Umlaute) . If I substitute these for oe as in 'Koeln' or ue the airports are recognized, but then automatically changed to the proper German spelling, that the system can't read.

All this works fine with Hamburg, Frankfurt or Stuttgart.

Interestingly the webpage accepts München, but changes it to Munich, Germany (MUC), not to München, Deutschland (MUC).

I think here is some room for improvement, especially for travelers, that are not familiar with airport codes.