Sala was on his way to Cardiff City on January 21, 2019 after signing from French club Nantes for £15million (€20m) when his plane came down over the English Channel, killing the Argentine striker, 28, and the pilot, Ibbotson, 59.
The court was told that Henderson, 67, had arranged the flight with football agent William McKay, and had asked Mr Ibbotson to fly the plane as he was in Paris on holiday.
Mr Ibbotson – who did not hold a commercial pilot's licence – was not qualified to fly at night and his rating to fly the single-engine Piper Malibu had expired.
A jury of seven men and five women were told that moments after finding out about the incident, Henderson contacted numerous people to ask them to stay silent, saying that it would "open a can of worms".
Henderson was convicted at Cardiff Crown Court on Thursday after the jury took seven and a half hours to come to a verdict.
Sala’s family were not present at the trial, but Daniel Machover of Hickman & Rose solicitors – who have been working on their behalf – released a statement regarding the outcome.
The statement read: "Mr Henderson’s convictions are welcome and we hope the CAA will ensure that illegal flights of this kind are stopped.
"The actions of David Henderson are only one piece in the puzzle of how the plane David Ibbotson was illegally flying came to crash into the sea on 21 January 2019.
"We still do not know the key information about the maintenance history of the aircraft and all the factors behind the carbon monoxide poisoning revealed in August 2019 by AAIB.
"The answers to these questions can only be properly established at Emiliano's inquest, which is due to start in February next year.
"The Sala family fervently hope that everyone involved in the inquest will provide full disclosure of material without further delay, including Piper Aircraft Inc and the AAIB.
"This should ensure that the inquest can fulfil its function of fully and fearlessly examining the evidence so that all the facts emerge.
"Only if that happens will Emiliano's family finally know the truth about this tragedy enabling all the lessons to be learned, so that no family goes through a similar preventable death."