Argentinian footballer Emiliano Sala, who recently signed a £15m deal at Cardiff City, is believed to have been one of two people on board the private aircraft.
French media are reporting the 28-year-old striker was on board when it disappeared from radar on Monday night while flying from Nantes to Cardiff.
Cardiff City chairman Mehmet Dalman said: “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."
French maritime authorities today said that a light aircraft lost radar contact over the English channel late on Monday, but could not confirm whether Cardiff City soccer player Emiliano Sala was on board.
The British coastguard said in a statement that it was assisting Guernsey Coastguard with a search for a light aircraft missing off Alderney in the Channel Islands, but that the plane had not yet been found.
Guernsey Police said: "A search and rescue operation is currently underway off the north of Alderney after a light aircraft disappeared from radar several hours ago.
"Two helicopters alongside the Guernsey and Alderney lifeboats are searching for it."
The Alderney lifeboat said it launched at 8.50pm on Monday night.