The American's defeat means that fur of the top 10 women's seeds have already been knocked out of Roland Garros
Two planes scoured an area northwest of the Channel Island of Alderney where unidentified debris was earlier spotted, but rescuers said chances of finding Cardiff City-bound Sala or the pilot alive were fading fast.
"We're up there looking for stuff that we don't expect to find," John Fitzgerald, chief officer of the Channel Islands Air Search told Reuters.
"If there was anything on the surface I think we would have found it on the first night because the weather conditions were really good."
The 28-year-old Argentina-born forward was flying from Nantes in western France to Cardiff for his debut with his Premier League club.
In a chilling voice message sent to friends, which Argentina's Clarin newspaper said was authenticated by Sala's father, Horacio, the player expressed concerns about the single-engine Piper Malibu aircraft he was flying in.
"I'm in the plane and it looks like it's going to fall apart," he said. "Dad, I'm really scared."
Air traffic controllers had guided searchers along the path flown by the light aircraft before it disappeared from radar screens at just over 2,000 feet (600 metres), Fitzgerald said.
Sala joined struggling Cardiff from FC Nantes last week for a club record fee of about 17 million euros ($19 million), having scored 12 goals for the French club this season.
"R.I.P Bro"
Both clubs were fearing the worst.
Cardiff City fans laid tributes outside their stadium to a player they barely knew but had built high hopes around.
"Sala a Bluebird. R.I.P. Bro. Big Love," read one, in reference to the team's nickname.
In Nantes, supporters laid rows of yellow flowers and held club scarves aloft in the city centre late on Tuesday.
The plane had been cruising at 5,000 feet (1,525 m) when the pilot requested to descend to a lower altitude on passing Guernsey. It lost radar contact at 2,300 feet (700 m), Guernsey police said.
Channel Island Air Search's Fitzgerald said the pilot had filed a 'VFR' flight plan, which requires pilots to avoid bad weather, have sight of the ground, and stay out of certain air corridors.
Police on Tuesday said the chance of finding survivors was slim and the prospect appeared bleaker a day later, with the water temperature in the Channel barely 10 degrees centigrade.
"There's no chance. You'd have to be really, really fit to survive even four or five hours in the water," Fitzgerald said.
British media on Wednesday cited Cardiff chairman Mehmet Dalman as saying the club had not organised Sala's travel plans. "He declined and made his own arrangements."
The American's defeat means that fur of the top 10 women's seeds have already been knocked out of Roland Garros
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