Argentinian footballer Emiliano Sala was on board a plane that went missing over the English Channel on Monday night, according to the French civil aviation authority.
The 28-year-old Nantes striker was announced as a new signing for Premier League club Cardiff City on Saturday.
The French civil aviation authority said Sala was aboard a light aircraft that disappeared from radar en route from Nantes to Cardiff.
Rescue teams were scrambled to waters north of Guernsey after the light aircraft carrying two people vanished, Guernsey Police said.
Searches of the area resumed on Tuesday morning, with authorities saying the missing plane had yet to be found.
Emiliano Sala's latest Instagram post, in which he says 'ciao' to his old team FC Nantes
Guernsey Police said the Piper PA-46 Malibu, a single turbine engine aircraft carrying two people, departed Nantes at 7.15pm for Cardiff and was flying at an altitude of 5,000ft.
On passing Guernsey it "requested descent", but Jersey air traffic control (ATC) lost contact with the plane while it was flying at 2,300ft.
Guernsey Coastguard received an alert at 8.23pm from Jersey ATC that a light aircraft had gone off their radar approximately 15 miles north of Guernsey.
A major search and rescue operation was triggered involving both St Peter Port and Alderney lifeboats and the Air Search 1 and two HM Coastguard helicopters.
An update from Guernsey Police said: "The search was terminated at 02:00, with all search and rescue assets being stood down, due to strengthening winds, worsening sea conditions and reducing visibility.
"At this time no trace of the missing aircraft had been found."
Air Search 1 and a French rescue helicopter based in Cherbourg resumed the search of the area at 8am on Tuesday.
Cardiff chairman Mehmet Dalman told the Mirror: "We are very concerned by the latest news that a light aircraft lost contact over the Channel last night.
"We are awaiting confirmation before we can say anything further. We are very concerned for the safety of Emiliano Sala."
A photo posted on Sala's Instagram account on Monday appears to show him with his Nantes team-mates and the caption includes the word "ciao".