German Pilot 1 seems to be the only one who knows about Langen Radar (instead of Dusseldorf)...
But the text will still be DUSSELDORF RADAR (unless you change it in captions.ini) and the boundaries will probably be wrong (unless you adjust them in Data/CenterSectors.dat). I just assume this plays in an alternative reality
And while we're on these nasty details: Shouldn't US Airways be called "Cactus"?
According to
https://en.wikipedia.org/wiki/US_Airways they no longer have a callsign, because they merged with AAL in 2015, but before that they had Cactus.
The callsign "US Air" is pfac97, "Cactus" is pfac84, so you just have to change Data/pf3_callsigns.dat:
to