USAFE KC-135R (62-3551 according ads-b) from Mildenhall in the track between Köln and Kleve, near the Dutch-German border.
Hearing them on 306.400.
BAF501 flight has confirmed the following serials:
BAF501 FA-103
BAF502 FA-116
BAF503 FA-081
BAF504 FA-124
BAF511 flight of 2 is also joining.