Search of the seabed is due to begin this weekend
Two seat cushions have been found that are likely to have come from the plane carrying missing Cardiff City striker Emiliano Sala, UK investigators said.
The cushions were found on a beach near Surtainville in Normandy, France, directly east of Guernsey where the plane disappeared from radar on 21 January.
Sala and the English pilot, Dave Ibbotson, have not been seen since and Guernsey Police says their chances of survival are "extremely remote".
The Air Accidents Investigation Bureau (AAIB) was advised by its French counterparts that the cushions were discovered on Monday.
"From a preliminary examination we have concluded that it is likely that the cushions are from the missing aircraft," an AAIB statement said.
It added that the AAIB has now identified a "priority search area of approximately four square nautical miles" and have commissioned a specialist survey vessel to carry out an underwater survey of the seabed to try to locate and identify possible aircraft wreckage.
The UK's Ministry of Defence's Salvage and Marine Operations Project Team organised the vessel, it said.
However, due to bad weather and sea conditions experts do not expect the underwater seabed search to begin until the end of the weekend.
The official hunt for the Piper PA-46 Malibu plane was called off on Thursday after three days of scouring the English Channel, but the AAIB announced it will restart the search this weekend.
It should take up to three days to use side-scan sonar equipment, which creates an image of large areas of the sea floor, to try to locate the wreckage which, if found, will be examined by a remotely operated vehicle.
The AAIB said it is aware that a private search, funded by more than £259,000 in public donations, is also being conducted in the area.
"We are liaising closely with those involved to maximise the chance of locating any wreckage and ensure a safe search operation," it said.
The AAIB added: "From the moment we were notified of the missing aircraft, we have been looking at the feasibility of conducting an underwater seabed search for aircraft wreckage."
They identified the search area after a "detailed assessment of the flight path and last known radar position".
Just two days before the plane went missing, Sala signed for Cardiff City in a club record deal.
The Argentine had been travelling to Wales after saying goodbye to teammates at FC Nantes.