My flight (in Spain) was delayed for 6h and after I submitted the claim the airline worker answered me that it was delayed due to KALP114A regulations imposed by ATC, but I didn't find any info, that such regulation even exists.
the regulation KALP114A, which caused delay, was introduced directly on the flight by Air Traffic Controllers
The flight was on the 14th of April, 2019, from Spain to Germany.
Within Europe, whenever there is need to reduce the number of flights through a certain airspace, the Network Manager (Eurocontrol) puts in a so called "regulation". This results in flights planned through the regulated airspace being delayed or re-routed.
Regulations are given an ID; those starting with KALP are from the Karlsruhe Upper Area Control (EDUU), southern sectors (Alps) above Flight Level 315.
Since your flight was over three weeks ago, I can't check the exact "regulation Id" in the public database, but it is likely that it was related to staffing issues at Karlsruhe upper area control centre.
An example of a current regulation starting with "KALP" is below:
Karlsruhe UAC has severe staffing problems and is causing many traffic delays this year.
A delay of 6 hours due to a regulation sounds extreme to me. I don't know what the origin and destination of the flight was, but typically a re-routing avoids the regulated airspace with only a short delay.
