French club Nantes have demanded payment of the £15m transfer fee for Emiliano Sala to join Cardiff City.
The 28-year-old striker who is presumed dead, went missing with Sala and pilot David Ibbotson on board two weeks ago.
Investigators have discovered the plane in the English Channel with a body inside but have yet to identify who it is because of the poor weather.
They are also trying to establish who owned the plane, insurance issues and other details surrounding the flight which may mean it results in an insurance pay out.
According to Sky Sports, Nantes are threatening legal actions against Cardiff over the Emiliano Sala transfer.
MySportDab report Nantes sent an e-mail demanding the £15m fee last Thursday and followed up with a legal letter on Tuesday.
They are threatening further action unless they get the first payment – the fee is spread over three years -within ten days