Nantes have appealed to FIFA after Cardiff City failed to meet the deadline for the first £5million payment of Emiliano Sala’s transfer fee.
The first payment for the Argentine striker, who died in a plane crash in the English Channel on January 21, had been due on Tuesday.
But the Premier League club are withholding payment until crash investigations were completed and they were satisfied over ‘anomalies’ around the deal.
Sala’s transfer fee of £15m had been due to be paid in three installments and Nantes wrote to Cardiff on February 5 requesting the first of them by February 20.
The clubs later agreed to extend the deadline but that has now passed without movement on Cardiff’s side.
Nantes have now contacted world football’s governing body to arbitrate in the matter.
A FIFA statement read: “We can confirm that we have received yesterday evening a claim from FC Nantes against Cardiff City in connection with the transfer of Emiliano Sala.
“We are looking into the matter and consequently we have no further comments at this stage.”
The 28-year-old Sala was Cardiff’s record signing and was due to report to the club for training on January 22.
But the Malibu Piper N264DB light aircraft carrying Sala and pilot David Ibbotson from Nantes to the Welsh capital went missing near the Channel Islands on January 21.
Sala’s body was found in the wreckage of the plane 13 days after it vanished but the body of Ibbotson has still not been located.
Cardiff chairman Mehmet Dalman has said that Cardiff will be ‘honourable’ with Nantes if they are contractually obliged to pay them the transfer fee.
Fellow French club Bordeaux are due 50 percent of the fee because of a sell-on clause in the deal with Nantes back in 2015.
Sportsmail reported that a preliminary report into the crash has raised questions about whether the pilot was legally licensed to carry the player, in a development that could encourage Cardiff to continue withholding payment.
The Air Accident Investigation Branch (AAIB) report says the Piper Malibu aircraft was not licensed for commercial use.
Pilot Mr Ibbotson, who died along with Sala in the plane, was entitled to transport the player on a private basis.
But to do so he would have needed to pay at least half the operating costs of the flight, under aviation rules governing the carrying of passengers.
The rules – which allow non-commercial pilots to gain experience by take passengers on a ‘cost sharing’ basis – also dictate that he needed to have had ‘a bona fide purpose for making the flight’ other than carrying Sala.
“The flight must not be made for the purpose of merely transporting the passenger,” the AAIB report stated.
There is no known evidence that Ibbotson was making the trip to France for any reason other than taking the player.
He was called upon to make the journey at the last minute when Sala – in need of a jet to get home on Saturday, January 19 – made it clear at 7.45pm the previous day that he had found no way of making the trip.
Agent Willie McKay, mandated by Nantes to find a buyer for Sala, asked his regular first-choice pilot David Henderson to make the flight but he was unavailable.