BBC Wales are running this interesting story.
There are calls for a series of flights in the weeks before the fatal crash which killed footballer Emiliano Sala to be investigated by regulators.
The aviation trade body Air Charter Association told BBC Wales it believes there are grounds to investigate other flights linked to the £15m transfer.
These carried Sala, his agent, Cardiff City officials and others between the UK and France in December and January.
In an exclusive interview with BBC Wales, Dave Edwards, chief executive officer of the Air Charter Association (Baca), warned that the "underground growth" of illegal and so-called "grey" charter flights was undermining legitimate air charter companies and putting passengers at risk.
These relate to flights which are not properly licensed under regulations governing aircraft and pilots.
He said the organisation's concerns about the sector date back about seven years and that they hold regular meetings with both the Civil Aviation Authority (CAA) and the European Union Aviation Safety Agency (Easa) to discuss the issue.
Mr Edwards said: "The football agent has said on the record that they paid for a series of flights.
"We've done some background research into all of those flights and we're concerned more than ever that all of them have the potential to have, certainly, questions to be asked about them, which is what we've pushed the CAA to be doing recently and also Easa because the origin of the flight was in France so that comes under (their) territory.
"There's enough circumstantial evidence here that would make us push the authorities to do a full investigation into the background to ensure it was compliant."
Baca has done its own research through the European air traffic control agency and established the various operators and pilots for the flights linked to the Sala deal.
https://www.bbc.com/news/uk-wales-47612188