Channel Islands Air Search has confirmed the operation has now shifted from a rescue to a recovery.
Chief officer John Fitzgerald said: “I think very much it is that sort of recovery stage now. It’s trying to find parts of the aircraft, whatever is floating on the surface.”
He added: “Sadly, I really don’t think, personally, there is any hope.
“At this time of year the conditions out there are pretty horrendous if you are actually in the water.”
The 28-year-old Argentinian was being flown to the UK by Dave Ibbotson, a 60-year-old pilot from Crowle in Lincolnshire, when the single-engined Piper PA-46 Malibu lost contact with air traffic controllers near Alderney on Monday evening.
Guernsey Police said rescue crews were focusing their search on the chance that the missing men could have landed on water and made it into the plane’s life raft.
Other options where they could have survived have also been suggested. These include that the pair were picked up by a passing ship but have not made contact and that the plane landed elsewhere.
However, officers admitted the possibility the two men survived is “slim”, with the most likely scenario that they died at sea after the plane hit the water and broke up.
Mr Sala was due to start training at Cardiff on Tuesday after signing a £15 million transfer deal from French club Nantes last weekend.
The striker reportedly voiced fears about the safety of the missing plane in an audio message he sent to friends in France during the flight.
In the WhatsApp message, a voice – believed to be Mr Sala’s – is heard saying in Spanish: “I’m up here on a plane that looks like it’s falling apart.”
He later adds: “I’m scared.”
Other reports have suggested the pilot made four attempts to take off before finally getting airborne at 7:15pm on Monday.
This came after Mr Ibbotson joked on social media when he arrived in France at the weekend that he was “a bit rusty” with the aircraft’s instrument landing system.
The plane had been flying at 5,000ft but requested to land while passing Guernsey. It was last detected at 2,300ft, losing contact with Jersey air traffic controllers near Casquets lighthouse at 8:30pm.
Coastguard helicopters and lifeboats have spent the past two days scouring seas and coastlines in the area.
A decision will be made today whether to call off the operation.
Cardiff supporters left tributes at the ground to mark their respect.
Chief executive Ken Choo said: “We would like to thank our fans, and the entire footballing family, for their support at this difficult time. We pray for positive news.”