"The water is very cold at the moment, the sea conditions are very rough out there, the wind is very strong," John Fitzgerald, chief officer of Channel Island Air Search, told AFP on Wednesday. "I think even the most hardened person out there – they'd have to be really tough to survive those conditions for the length of time that they'd been there."
Sala, who signed on Saturday from French club Nantes for a reported fee of 17 million euros (US$19.3 million), was flying to Cardiff in a single-engine Piper PA-46 Malibu aircraft.
Britain's Air Accidents Investigation Branch (AAIB), which is probing the disappearance, said the plane was registered in the United States.
Two days of searches covering a swathe of the Channel around Guernsey – which sits off the north coast of France – led to sightings of "a number of floating objects in the water," police have previously said.
The Guernsey coastguard on Wednesday named the pilot, the only other person in the plane, as David Ibbotson.
British media said he was a 60-year-old married father of three and lived in Scunthorpe in northern England.
"I can't tell you who arranged the flight because I don't know."
In Sala's Argentine hometown of Progreso, his father Horacio told the press on Tuesday that as "the hours go by and I don't know anything, it makes me fear the worst".
The striker, who had been at Nantes since 2015 and had scored 13 goals in all competitions this season, had signed a three-and-a-half-year contract with relegation-threatened Cardiff subject to receiving international clearance.