According to airliners.de, the passenger booked a business class ticket from Oslo to Seattle via Frankfurt €657.
On the return flight, the passenger flew from Frankfurt to Berlin on a separate ticket. Lufthansa is claiming he should have paid €2769 and is demanding €2112 plus interest.
Its lawsuit has been thrown out by the German courts because it could not understand how Lufthansa reached the compensation figure.
But according to airliners.de, Lufthansa is appealing the decision.
Lufthansa said it could not comment as this ‘is a running court case’.
There has been a rise in passengers making use of loopholes to get cheap flights, known as skiplagging.
A dedicated website, called Skiplagged, even promises to ‘find flights the airlines don’t want you to see’.
It uses algorithms to show the cheapest flights and hidden-city flights and claims it can find travellers savings of up to 80%.
Its homepage says: “Our flights are so cheap, United sued us… but we won.”
In 2015 United tried to sue the website’s founder, Aktarer Zaman, then 22, but the judge threw out the case, although it was on ‘procedural grounds’.
At the end of last year United began writing to passengers it had identified as exploiting the system demanding they pay back the difference in fare or risk being refused the right to board a United flight and lose their frequent flyer membership.