Travel time over the 80 km (50 mi) railway is around 75 minutes with a maximum speed of 120 km/h (75 mph).

North of the Schlei, the line runs through the typical landscape of Angeln, the location of the station of Süderbrarup.

The Kiel-Eckernförde-Flensburger Eisenbahn-Gesellschaft (KEFE) was founded on 13 June 1878 in Kiel by the Prussian government, the local municipalities, and some individual investors.

On 19 August 1878, little over two months later, the society received a concession to operate a standard-gauge railway from Kiel to Flensburg, running parallel to the Baltic Sea coast.

In 1986, the line received an hourly service for the first time, and the next year, all minor stations were closed (Kiel-Hassee, Kronshagen, (Kiel-)Suchsdorf, Neuwittenbek, Altenhof, Lindaunis, Mohrkirch, Winderatt, Husby und Maasbüll).

In late 2007, the station at Kiel-Hassee was reopened (but 250 meters north of the old location, next to a new shopping mall), as Husby and Kiel-Suchsdorf had been several years earlier.