Thomas Cook Group who own German airline Condor, are said to be furious over the Ryan Air deal with LaudaMotion.
Ryan Air are acquiring 24.9% of LaudaMotion (ex-AirBerlin subsidiary Niki), with the intention of taking that ownership to 75% once regulatory hurdles are overcome.
Condor was involved with several other airlines in contracting to use LaudaMotion aircraft to ease summer/winter schedules.
However it sees Ryan Air as a major competitor and is uncomfortable with the business arrangement.
Ryan Air recently started a new subsidiary in Poland designed to compete directly with holiday and summer/winter sun airlines.